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jdk/src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp
Kelvin Nilsen 26296f5dbb no need to set_mutator_free_after_updaterefs
2026-01-27 19:52:25 +00:00

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/*
* Copyright (c) 2016, 2021, Red Hat, Inc. All rights reserved.
* Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
* Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "gc/shared/tlab_globals.hpp"
#include "gc/shenandoah/shenandoahAffiliation.hpp"
#include "gc/shenandoah/shenandoahFreeSet.hpp"
#include "gc/shenandoah/shenandoahHeap.inline.hpp"
#include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
#include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
#include "gc/shenandoah/shenandoahOldGeneration.hpp"
#include "gc/shenandoah/shenandoahSimpleBitMap.inline.hpp"
#include "gc/shenandoah/shenandoahYoungGeneration.hpp"
#include "logging/logStream.hpp"
#include "memory/resourceArea.hpp"
#include "runtime/orderAccess.hpp"
static const char* partition_name(ShenandoahFreeSetPartitionId t) {
switch (t) {
case ShenandoahFreeSetPartitionId::NotFree: return "NotFree";
case ShenandoahFreeSetPartitionId::Mutator: return "Mutator";
case ShenandoahFreeSetPartitionId::Collector: return "Collector";
case ShenandoahFreeSetPartitionId::OldCollector: return "OldCollector";
default:
ShouldNotReachHere();
return "Unrecognized";
}
}
class ShenandoahLeftRightIterator {
private:
idx_t _idx;
idx_t _end;
ShenandoahRegionPartitions* _partitions;
ShenandoahFreeSetPartitionId _partition;
public:
explicit ShenandoahLeftRightIterator(ShenandoahRegionPartitions* partitions,
ShenandoahFreeSetPartitionId partition, bool use_empty = false)
: _idx(0), _end(0), _partitions(partitions), _partition(partition) {
_idx = use_empty ? _partitions->leftmost_empty(_partition) : _partitions->leftmost(_partition);
_end = use_empty ? _partitions->rightmost_empty(_partition) : _partitions->rightmost(_partition);
}
bool has_next() const {
if (_idx <= _end) {
assert(_partitions->in_free_set(_partition, _idx), "Boundaries or find_last_set_bit failed: %zd", _idx);
return true;
}
return false;
}
idx_t current() const {
return _idx;
}
idx_t next() {
_idx = _partitions->find_index_of_next_available_region(_partition, _idx + 1);
return current();
}
};
class ShenandoahRightLeftIterator {
private:
idx_t _idx;
idx_t _end;
ShenandoahRegionPartitions* _partitions;
ShenandoahFreeSetPartitionId _partition;
public:
explicit ShenandoahRightLeftIterator(ShenandoahRegionPartitions* partitions,
ShenandoahFreeSetPartitionId partition, bool use_empty = false)
: _idx(0), _end(0), _partitions(partitions), _partition(partition) {
_idx = use_empty ? _partitions->rightmost_empty(_partition) : _partitions->rightmost(_partition);
_end = use_empty ? _partitions->leftmost_empty(_partition) : _partitions->leftmost(_partition);
}
bool has_next() const {
if (_idx >= _end) {
assert(_partitions->in_free_set(_partition, _idx), "Boundaries or find_last_set_bit failed: %zd", _idx);
return true;
}
return false;
}
idx_t current() const {
return _idx;
}
idx_t next() {
_idx = _partitions->find_index_of_previous_available_region(_partition, _idx - 1);
return current();
}
};
#ifndef PRODUCT
void ShenandoahRegionPartitions::dump_bitmap() const {
log_debug(gc)("Mutator range [%zd, %zd], Collector range [%zd, %zd"
"], Old Collector range [%zd, %zd]",
_leftmosts[int(ShenandoahFreeSetPartitionId::Mutator)],
_rightmosts[int(ShenandoahFreeSetPartitionId::Mutator)],
_leftmosts[int(ShenandoahFreeSetPartitionId::Collector)],
_rightmosts[int(ShenandoahFreeSetPartitionId::Collector)],
_leftmosts[int(ShenandoahFreeSetPartitionId::OldCollector)],
_rightmosts[int(ShenandoahFreeSetPartitionId::OldCollector)]);
log_debug(gc)("Empty Mutator range [%zd, %zd"
"], Empty Collector range [%zd, %zd"
"], Empty Old Collecto range [%zd, %zd]",
_leftmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)],
_rightmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)],
_leftmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)],
_rightmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)],
_leftmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)],
_rightmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)]);
log_debug(gc)("%6s: %18s %18s %18s %18s", "index", "Mutator Bits", "Collector Bits", "Old Collector Bits", "NotFree Bits");
dump_bitmap_range(0, _max-1);
}
void ShenandoahRegionPartitions::dump_bitmap_range(idx_t start_region_idx, idx_t end_region_idx) const {
assert((start_region_idx >= 0) && (start_region_idx < (idx_t) _max), "precondition");
assert((end_region_idx >= 0) && (end_region_idx < (idx_t) _max), "precondition");
idx_t aligned_start = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].aligned_index(start_region_idx);
idx_t aligned_end = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].aligned_index(end_region_idx);
idx_t alignment = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].alignment();
while (aligned_start <= aligned_end) {
dump_bitmap_row(aligned_start);
aligned_start += alignment;
}
}
void ShenandoahRegionPartitions::dump_bitmap_row(idx_t region_idx) const {
assert((region_idx >= 0) && (region_idx < (idx_t) _max), "precondition");
idx_t aligned_idx = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].aligned_index(region_idx);
uintx mutator_bits = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].bits_at(aligned_idx);
uintx collector_bits = _membership[int(ShenandoahFreeSetPartitionId::Collector)].bits_at(aligned_idx);
uintx old_collector_bits = _membership[int(ShenandoahFreeSetPartitionId::OldCollector)].bits_at(aligned_idx);
uintx free_bits = mutator_bits | collector_bits | old_collector_bits;
uintx notfree_bits = ~free_bits;
log_debug(gc)("%6zd : " SIZE_FORMAT_X_0 " 0x" SIZE_FORMAT_X_0 " 0x" SIZE_FORMAT_X_0 " 0x" SIZE_FORMAT_X_0,
aligned_idx, mutator_bits, collector_bits, old_collector_bits, notfree_bits);
}
#endif
ShenandoahRegionPartitions::ShenandoahRegionPartitions(size_t max_regions, ShenandoahFreeSet* free_set) :
_max(max_regions),
_region_size_bytes(ShenandoahHeapRegion::region_size_bytes()),
_free_set(free_set),
_membership{ ShenandoahSimpleBitMap(max_regions), ShenandoahSimpleBitMap(max_regions) , ShenandoahSimpleBitMap(max_regions) }
{
initialize_old_collector();
make_all_regions_unavailable();
}
void ShenandoahFreeSet::account_for_pip_regions(size_t mutator_regions, size_t mutator_bytes,
size_t collector_regions, size_t collector_bytes) {
shenandoah_assert_heaplocked();
// We have removed all of these regions from their respective partition. Each pip region is "in" the NotFree partition.
// We want to account for all pip pad memory as if it had been consumed from within the Mutator partition.
//
// After we finish promote in place, the pad memory will be deallocated and made available within the OldCollector
// region. At that time, we will transfer the used memory from the Mutator partition to the OldCollector parttion,
// and then we will unallocate the pad memory.
_partitions.decrease_region_counts(ShenandoahFreeSetPartitionId::Mutator, mutator_regions);
_partitions.decrease_region_counts(ShenandoahFreeSetPartitionId::Collector, collector_regions);
// Increase used by remnant fill objects placed in both Mutator and Collector partitions
_partitions.increase_used(ShenandoahFreeSetPartitionId::Mutator, mutator_bytes);
_partitions.increase_used(ShenandoahFreeSetPartitionId::Collector, collector_bytes);
// Now transfer all of the memory contained within Collector pip regions from the Collector to the Mutator.
// Each of these regions is treated as fully used, even though some of the region's memory may be artifically used,
// to be recycled and put into allocatable OldCollector partition after the region has been promoted in place.
_partitions.transfer_used_capacity_from_to(ShenandoahFreeSetPartitionId::Collector, ShenandoahFreeSetPartitionId::Mutator,
collector_regions);
// Conservatively, act as if we've promoted from both Mutator and Collector partitions
recompute_total_affiliated</* MutatorEmptiesChanged */ false, /* CollectorEmptiesChanged */ false,
/* OldCollectorEmptiesChanged */ false, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ true, /* OldCollectorSizeChanged */ false,
/* AffiliatedChangesAreYoungNeutral */ true, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ false>();
recompute_total_young_used</* UsedByMutatorChanged */ true, /*UsedByCollectorChanged */ true>();
recompute_total_global_used</* UsedByMutatorChanged */ true, /* UsedByCollectorChanged */ true,
/* UsedByOldCollectorChanged */ false>();
}
ShenandoahFreeSetPartitionId ShenandoahFreeSet::prepare_to_promote_in_place(size_t idx, size_t bytes) {
shenandoah_assert_heaplocked();
size_t min_remnant_size = PLAB::min_size() * HeapWordSize;
ShenandoahFreeSetPartitionId p = _partitions.membership(idx);
if (bytes >= min_remnant_size) {
assert((p == ShenandoahFreeSetPartitionId::Mutator) || (p == ShenandoahFreeSetPartitionId::Collector),
"PIP region must be associated with young");
_partitions.raw_clear_membership(idx, p);
} else {
assert(p == ShenandoahFreeSetPartitionId::NotFree, "We did not fill this region and do not need to adjust used");
}
return p;
}
inline bool ShenandoahFreeSet::can_allocate_from(ShenandoahHeapRegion *r) const {
return r->is_empty() || (r->is_trash() && !_heap->is_concurrent_weak_root_in_progress());
}
inline bool ShenandoahFreeSet::can_allocate_from(size_t idx) const {
ShenandoahHeapRegion* r = _heap->get_region(idx);
return can_allocate_from(r);
}
inline size_t ShenandoahFreeSet::alloc_capacity(ShenandoahHeapRegion *r) const {
if (r->is_trash()) {
// This would be recycled on allocation path
return ShenandoahHeapRegion::region_size_bytes();
} else {
return r->free();
}
}
inline size_t ShenandoahFreeSet::alloc_capacity(size_t idx) const {
ShenandoahHeapRegion* r = _heap->get_region(idx);
return alloc_capacity(r);
}
inline bool ShenandoahFreeSet::has_alloc_capacity(ShenandoahHeapRegion *r) const {
return alloc_capacity(r) > 0;
}
// This is used for unit testing. Do not use in production code.
void ShenandoahFreeSet::resize_old_collector_capacity(size_t regions) {
shenandoah_assert_heaplocked();
size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
size_t original_old_regions = _partitions.get_capacity(ShenandoahFreeSetPartitionId::OldCollector) / region_size_bytes;
size_t unaffiliated_mutator_regions = _partitions.get_empty_region_counts(ShenandoahFreeSetPartitionId::Mutator);
size_t unaffiliated_collector_regions = _partitions.get_empty_region_counts(ShenandoahFreeSetPartitionId::Collector);
size_t unaffiliated_old_collector_regions = _partitions.get_empty_region_counts(ShenandoahFreeSetPartitionId::OldCollector);
if (regions > original_old_regions) {
size_t regions_to_transfer = regions - original_old_regions;
if (regions_to_transfer <= unaffiliated_mutator_regions + unaffiliated_collector_regions) {
size_t regions_from_mutator =
(regions_to_transfer > unaffiliated_mutator_regions)? unaffiliated_mutator_regions: regions_to_transfer;
regions_to_transfer -= regions_from_mutator;
size_t regions_from_collector = regions_to_transfer;
if (regions_from_mutator > 0) {
transfer_empty_regions_from_to(ShenandoahFreeSetPartitionId::Mutator, ShenandoahFreeSetPartitionId::OldCollector,
regions_from_mutator);
}
if (regions_from_collector > 0) {
transfer_empty_regions_from_to(ShenandoahFreeSetPartitionId::Collector, ShenandoahFreeSetPartitionId::OldCollector,
regions_from_mutator);
}
} else {
fatal("Could not resize old for unit test");
}
} else if (regions < original_old_regions) {
size_t regions_to_transfer = original_old_regions - regions;
if (regions_to_transfer <= unaffiliated_old_collector_regions) {
transfer_empty_regions_from_to(ShenandoahFreeSetPartitionId::OldCollector, ShenandoahFreeSetPartitionId::Mutator,
regions_to_transfer);
} else {
fatal("Could not resize old for unit test");
}
}
// else, old generation is already appropriately sized
}
void ShenandoahFreeSet::reset_bytes_allocated_since_gc_start(size_t initial_bytes_allocated) {
shenandoah_assert_heaplocked();
// Future inquiries of get_total_bytes_allocated() will return the sum of
// _total_bytes_previously_allocated and _mutator_bytes_allocated_since_gc_start.
// Since _mutator_bytes_allocated_since_gc_start does not start at zero, we subtract initial_bytes_allocated so as
// to not double count these allocated bytes.
size_t original_mutator_bytes_allocated_since_gc_start = _mutator_bytes_allocated_since_gc_start;
// Setting _mutator_bytes_allocated_since_gc_start before _total_bytes_previously_allocated reduces the damage
// in the case that the control or regulator thread queries get_bytes_allocated_since_previous_sample() between
// the two assignments.
//
// These are not declared as volatile so the compiler or hardware may reorder the assignments. The implementation of
// get_bytes_allocated_since_previous_cycle() is robust to this possibility, as are triggering heuristics. The current
// implementation assumes we are better off to tolerate the very rare race rather than impose a synchronization penalty
// on every update and fetch. (Perhaps it would be better to make the opposite tradeoff for improved maintainability.)
_mutator_bytes_allocated_since_gc_start = initial_bytes_allocated;
_total_bytes_previously_allocated += original_mutator_bytes_allocated_since_gc_start - initial_bytes_allocated;
}
void ShenandoahFreeSet::increase_bytes_allocated(size_t bytes) {
shenandoah_assert_heaplocked();
_mutator_bytes_allocated_since_gc_start += bytes;
}
inline idx_t ShenandoahRegionPartitions::leftmost(ShenandoahFreeSetPartitionId which_partition) const {
assert (which_partition < NumPartitions, "selected free partition must be valid");
idx_t idx = _leftmosts[int(which_partition)];
if (idx >= _max) {
return _max;
} else {
// Cannot assert that membership[which_partition.is_set(idx) because this helper method may be used
// to query the original value of leftmost when leftmost must be adjusted because the interval representing
// which_partition is shrinking after the region that used to be leftmost is retired.
return idx;
}
}
inline idx_t ShenandoahRegionPartitions::rightmost(ShenandoahFreeSetPartitionId which_partition) const {
assert (which_partition < NumPartitions, "selected free partition must be valid");
idx_t idx = _rightmosts[int(which_partition)];
// Cannot assert that membership[which_partition.is_set(idx) because this helper method may be used
// to query the original value of leftmost when leftmost must be adjusted because the interval representing
// which_partition is shrinking after the region that used to be leftmost is retired.
return idx;
}
void ShenandoahRegionPartitions::initialize_old_collector() {
_capacity[int(ShenandoahFreeSetPartitionId::OldCollector)] = 0;
_region_counts[int(ShenandoahFreeSetPartitionId::OldCollector)] = 0;
_empty_region_counts[int(ShenandoahFreeSetPartitionId::OldCollector)] = 0;
}
void ShenandoahRegionPartitions::make_all_regions_unavailable() {
shenandoah_assert_heaplocked_or_safepoint();
for (size_t partition_id = 0; partition_id < IntNumPartitions; partition_id++) {
_membership[partition_id].clear_all();
_leftmosts[partition_id] = _max;
_rightmosts[partition_id] = -1;
_leftmosts_empty[partition_id] = _max;
_rightmosts_empty[partition_id] = -1;;
_capacity[partition_id] = 0;
_region_counts[partition_id] = 0;
_empty_region_counts[partition_id] = 0;
_used[partition_id] = 0;
_humongous_waste[partition_id] = 0;
_available[partition_id] = 0;
}
}
void ShenandoahRegionPartitions::establish_mutator_intervals(idx_t mutator_leftmost, idx_t mutator_rightmost,
idx_t mutator_leftmost_empty, idx_t mutator_rightmost_empty,
size_t total_mutator_regions, size_t empty_mutator_regions,
size_t mutator_region_count, size_t mutator_used,
size_t mutator_humongous_waste_bytes) {
shenandoah_assert_heaplocked();
_leftmosts[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_leftmost;
_rightmosts[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_rightmost;
_leftmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_leftmost_empty;
_rightmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_rightmost_empty;
_region_counts[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_region_count;
_used[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_used;
_capacity[int(ShenandoahFreeSetPartitionId::Mutator)] = total_mutator_regions * _region_size_bytes;
_humongous_waste[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_humongous_waste_bytes;
_available[int(ShenandoahFreeSetPartitionId::Mutator)] =
_capacity[int(ShenandoahFreeSetPartitionId::Mutator)] - _used[int(ShenandoahFreeSetPartitionId::Mutator)];
_empty_region_counts[int(ShenandoahFreeSetPartitionId::Mutator)] = empty_mutator_regions;
_leftmosts[int(ShenandoahFreeSetPartitionId::Collector)] = _max;
_rightmosts[int(ShenandoahFreeSetPartitionId::Collector)] = -1;
_leftmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)] = _max;
_rightmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)] = -1;
_region_counts[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
_used[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
_capacity[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
_humongous_waste[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
_available[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
_empty_region_counts[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
}
void ShenandoahRegionPartitions::establish_old_collector_intervals(idx_t old_collector_leftmost,
idx_t old_collector_rightmost,
idx_t old_collector_leftmost_empty,
idx_t old_collector_rightmost_empty,
size_t total_old_collector_region_count,
size_t old_collector_empty, size_t old_collector_regions,
size_t old_collector_used,
size_t old_collector_humongous_waste_bytes) {
shenandoah_assert_heaplocked();
_leftmosts[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_leftmost;
_rightmosts[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_rightmost;
_leftmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_leftmost_empty;
_rightmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_rightmost_empty;
_region_counts[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_regions;
_used[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_used;
_capacity[int(ShenandoahFreeSetPartitionId::OldCollector)] = total_old_collector_region_count * _region_size_bytes;
_humongous_waste[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_humongous_waste_bytes;
_available[int(ShenandoahFreeSetPartitionId::OldCollector)] =
_capacity[int(ShenandoahFreeSetPartitionId::OldCollector)] - _used[int(ShenandoahFreeSetPartitionId::OldCollector)];
_empty_region_counts[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_empty;
}
void ShenandoahRegionPartitions::increase_used(ShenandoahFreeSetPartitionId which_partition, size_t bytes) {
shenandoah_assert_heaplocked();
assert (which_partition < NumPartitions, "Partition must be valid");
_used[int(which_partition)] += bytes;
_available[int(which_partition)] -= bytes;
assert (_used[int(which_partition)] <= _capacity[int(which_partition)],
"Must not use (%zu) more than capacity (%zu) after increase by %zu",
_used[int(which_partition)], _capacity[int(which_partition)], bytes);
}
void ShenandoahRegionPartitions::decrease_used(ShenandoahFreeSetPartitionId which_partition, size_t bytes) {
shenandoah_assert_heaplocked();
assert (which_partition < NumPartitions, "Partition must be valid");
assert (_used[int(which_partition)] >= bytes, "Must not use less than zero after decrease");
_used[int(which_partition)] -= bytes;
_available[int(which_partition)] += bytes;
}
void ShenandoahRegionPartitions::increase_humongous_waste(ShenandoahFreeSetPartitionId which_partition, size_t bytes) {
shenandoah_assert_heaplocked();
assert (which_partition < NumPartitions, "Partition must be valid");
_humongous_waste[int(which_partition)] += bytes;
}
size_t ShenandoahRegionPartitions::get_humongous_waste(ShenandoahFreeSetPartitionId which_partition) {
assert (which_partition < NumPartitions, "Partition must be valid");
return _humongous_waste[int(which_partition)];;
}
void ShenandoahRegionPartitions::set_capacity_of(ShenandoahFreeSetPartitionId which_partition, size_t value) {
shenandoah_assert_heaplocked();
assert (which_partition < NumPartitions, "selected free set must be valid");
_capacity[int(which_partition)] = value;
_available[int(which_partition)] = value - _used[int(which_partition)];
}
void ShenandoahRegionPartitions::set_used_by(ShenandoahFreeSetPartitionId which_partition, size_t value) {
shenandoah_assert_heaplocked();
assert (which_partition < NumPartitions, "selected free set must be valid");
_used[int(which_partition)] = value;
_available[int(which_partition)] = _capacity[int(which_partition)] - value;
}
void ShenandoahRegionPartitions::increase_capacity(ShenandoahFreeSetPartitionId which_partition, size_t bytes) {
shenandoah_assert_heaplocked();
assert (which_partition < NumPartitions, "Partition must be valid");
_capacity[int(which_partition)] += bytes;
_available[int(which_partition)] += bytes;
}
void ShenandoahRegionPartitions::transfer_used_capacity_from_to(ShenandoahFreeSetPartitionId from_partition,
ShenandoahFreeSetPartitionId to_partition, size_t regions) {
shenandoah_assert_heaplocked();
size_t bytes = regions * ShenandoahHeapRegion::region_size_bytes();
assert (from_partition < NumPartitions, "Partition must be valid");
assert (to_partition < NumPartitions, "Partition must be valid");
assert(_capacity[int(from_partition)] >= bytes, "Cannot remove more capacity bytes than are present");
assert(_used[int(from_partition)] >= bytes, "Cannot transfer used bytes that are not used");
// available is unaffected by transfer
_capacity[int(from_partition)] -= bytes;
_used[int(from_partition)] -= bytes;
_capacity[int(to_partition)] += bytes;
_used[int(to_partition)] += bytes;
}
void ShenandoahRegionPartitions::decrease_capacity(ShenandoahFreeSetPartitionId which_partition, size_t bytes) {
shenandoah_assert_heaplocked();
assert (which_partition < NumPartitions, "Partition must be valid");
assert(_capacity[int(which_partition)] >= bytes, "Cannot remove more capacity bytes than are present");
assert(_available[int(which_partition)] >= bytes, "Cannot shrink capacity unless capacity is unused");
_capacity[int(which_partition)] -= bytes;
_available[int(which_partition)] -= bytes;
}
void ShenandoahRegionPartitions::increase_available(ShenandoahFreeSetPartitionId which_partition, size_t bytes) {
shenandoah_assert_heaplocked();
assert (which_partition < NumPartitions, "Partition must be valid");
_available[int(which_partition)] += bytes;
}
void ShenandoahRegionPartitions::decrease_available(ShenandoahFreeSetPartitionId which_partition, size_t bytes) {
shenandoah_assert_heaplocked();
assert (which_partition < NumPartitions, "Partition must be valid");
assert(_available[int(which_partition)] >= bytes, "Cannot remove more available bytes than are present");
_available[int(which_partition)] -= bytes;
}
size_t ShenandoahRegionPartitions::get_available(ShenandoahFreeSetPartitionId which_partition) {
assert (which_partition < NumPartitions, "Partition must be valid");
return _available[int(which_partition)];;
}
void ShenandoahRegionPartitions::increase_region_counts(ShenandoahFreeSetPartitionId which_partition, size_t regions) {
_region_counts[int(which_partition)] += regions;
}
void ShenandoahRegionPartitions::decrease_region_counts(ShenandoahFreeSetPartitionId which_partition, size_t regions) {
assert(_region_counts[int(which_partition)] >= regions, "Cannot remove more regions than are present");
_region_counts[int(which_partition)] -= regions;
}
void ShenandoahRegionPartitions::increase_empty_region_counts(ShenandoahFreeSetPartitionId which_partition, size_t regions) {
_empty_region_counts[int(which_partition)] += regions;
}
void ShenandoahRegionPartitions::decrease_empty_region_counts(ShenandoahFreeSetPartitionId which_partition, size_t regions) {
assert(_empty_region_counts[int(which_partition)] >= regions, "Cannot remove more regions than are present");
_empty_region_counts[int(which_partition)] -= regions;
}
void ShenandoahRegionPartitions::one_region_is_no_longer_empty(ShenandoahFreeSetPartitionId partition) {
decrease_empty_region_counts(partition, (size_t) 1);
}
// All members of partition between low_idx and high_idx inclusive have been removed.
void ShenandoahRegionPartitions::shrink_interval_if_range_modifies_either_boundary(
ShenandoahFreeSetPartitionId partition, idx_t low_idx, idx_t high_idx, size_t num_regions) {
assert((low_idx <= high_idx) && (low_idx >= 0) && (high_idx < _max), "Range must span legal index values");
size_t span = high_idx + 1 - low_idx;
bool regions_are_contiguous = (span == num_regions);
if (low_idx == leftmost(partition)) {
assert (!_membership[int(partition)].is_set(low_idx), "Do not shrink interval if region not removed");
if (high_idx + 1 == _max) {
if (regions_are_contiguous) {
_leftmosts[int(partition)] = _max;
} else {
_leftmosts[int(partition)] = find_index_of_next_available_region(partition, low_idx + 1);
}
} else {
if (regions_are_contiguous) {
_leftmosts[int(partition)] = find_index_of_next_available_region(partition, high_idx + 1);
} else {
_leftmosts[int(partition)] = find_index_of_next_available_region(partition, low_idx + 1);
}
}
if (_leftmosts_empty[int(partition)] < _leftmosts[int(partition)]) {
// This gets us closer to where we need to be; we'll scan further when leftmosts_empty is requested.
_leftmosts_empty[int(partition)] = _leftmosts[int(partition)];
}
}
if (high_idx == _rightmosts[int(partition)]) {
assert (!_membership[int(partition)].is_set(high_idx), "Do not shrink interval if region not removed");
if (low_idx == 0) {
if (regions_are_contiguous) {
_rightmosts[int(partition)] = -1;
} else {
_rightmosts[int(partition)] = find_index_of_previous_available_region(partition, high_idx - 1);
}
} else {
if (regions_are_contiguous) {
_rightmosts[int(partition)] = find_index_of_previous_available_region(partition, low_idx - 1);
} else {
_rightmosts[int(partition)] = find_index_of_previous_available_region(partition, high_idx - 1);
}
}
if (_rightmosts_empty[int(partition)] > _rightmosts[int(partition)]) {
// This gets us closer to where we need to be; we'll scan further when rightmosts_empty is requested.
_rightmosts_empty[int(partition)] = _rightmosts[int(partition)];
}
}
if (_leftmosts[int(partition)] > _rightmosts[int(partition)]) {
_leftmosts[int(partition)] = _max;
_rightmosts[int(partition)] = -1;
_leftmosts_empty[int(partition)] = _max;
_rightmosts_empty[int(partition)] = -1;
}
}
void ShenandoahRegionPartitions::establish_interval(ShenandoahFreeSetPartitionId partition, idx_t low_idx,
idx_t high_idx, idx_t low_empty_idx, idx_t high_empty_idx) {
#ifdef ASSERT
assert (partition < NumPartitions, "invalid partition");
if (low_idx != max()) {
assert((low_idx <= high_idx) && (low_idx >= 0) && (high_idx < _max), "Range must span legal index values");
assert (in_free_set(partition, low_idx), "Must be in partition of established interval");
assert (in_free_set(partition, high_idx), "Must be in partition of established interval");
}
if (low_empty_idx != max()) {
ShenandoahHeapRegion* r = ShenandoahHeap::heap()->get_region(low_empty_idx);
assert (in_free_set(partition, low_empty_idx) && (r->is_trash() || r->free() == _region_size_bytes),
"Must be empty and in partition of established interval");
r = ShenandoahHeap::heap()->get_region(high_empty_idx);
assert (in_free_set(partition, high_empty_idx), "Must be in partition of established interval");
}
#endif
_leftmosts[int(partition)] = low_idx;
_rightmosts[int(partition)] = high_idx;
_leftmosts_empty[int(partition)] = low_empty_idx;
_rightmosts_empty[int(partition)] = high_empty_idx;
}
inline void ShenandoahRegionPartitions::shrink_interval_if_boundary_modified(ShenandoahFreeSetPartitionId partition,
idx_t idx) {
shrink_interval_if_range_modifies_either_boundary(partition, idx, idx, 1);
}
// Some members of partition between low_idx and high_idx inclusive have been added.
void ShenandoahRegionPartitions::
expand_interval_if_range_modifies_either_boundary(ShenandoahFreeSetPartitionId partition, idx_t low_idx, idx_t high_idx,
idx_t low_empty_idx, idx_t high_empty_idx) {
if (_leftmosts[int(partition)] > low_idx) {
_leftmosts[int(partition)] = low_idx;
}
if (_rightmosts[int(partition)] < high_idx) {
_rightmosts[int(partition)] = high_idx;
}
if (_leftmosts_empty[int(partition)] > low_empty_idx) {
_leftmosts_empty[int(partition)] = low_empty_idx;
}
if (_rightmosts_empty[int(partition)] < high_empty_idx) {
_rightmosts_empty[int(partition)] = high_empty_idx;
}
}
void ShenandoahRegionPartitions::expand_interval_if_boundary_modified(ShenandoahFreeSetPartitionId partition,
idx_t idx, size_t region_available) {
if (_leftmosts[int(partition)] > idx) {
_leftmosts[int(partition)] = idx;
}
if (_rightmosts[int(partition)] < idx) {
_rightmosts[int(partition)] = idx;
}
if (region_available == _region_size_bytes) {
if (_leftmosts_empty[int(partition)] > idx) {
_leftmosts_empty[int(partition)] = idx;
}
if (_rightmosts_empty[int(partition)] < idx) {
_rightmosts_empty[int(partition)] = idx;
}
}
}
void ShenandoahRegionPartitions::retire_range_from_partition(
ShenandoahFreeSetPartitionId partition, idx_t low_idx, idx_t high_idx) {
// Note: we may remove from free partition even if region is not entirely full, such as when available < PLAB::min_size()
assert ((low_idx < _max) && (high_idx < _max), "Both indices are sane: %zu and %zu < %zu",
low_idx, high_idx, _max);
assert (partition < NumPartitions, "Cannot remove from free partitions if not already free");
for (idx_t idx = low_idx; idx <= high_idx; idx++) {
#ifdef ASSERT
ShenandoahHeapRegion* r = ShenandoahHeap::heap()->get_region(idx);
assert (in_free_set(partition, idx), "Must be in partition to remove from partition");
assert(r->is_empty() || r->is_trash(), "Region must be empty or trash");
#endif
_membership[int(partition)].clear_bit(idx);
}
size_t num_regions = high_idx + 1 - low_idx;
decrease_region_counts(partition, num_regions);
decrease_empty_region_counts(partition, num_regions);
shrink_interval_if_range_modifies_either_boundary(partition, low_idx, high_idx, num_regions);
}
size_t ShenandoahRegionPartitions::retire_from_partition(ShenandoahFreeSetPartitionId partition,
idx_t idx, size_t used_bytes) {
size_t waste_bytes = 0;
// Note: we may remove from free partition even if region is not entirely full, such as when available < PLAB::min_size()
assert (idx < _max, "index is sane: %zu < %zu", idx, _max);
assert (partition < NumPartitions, "Cannot remove from free partitions if not already free");
assert (in_free_set(partition, idx), "Must be in partition to remove from partition");
if (used_bytes < _region_size_bytes) {
// Count the alignment pad remnant of memory as used when we retire this region
size_t fill_padding = _region_size_bytes - used_bytes;
waste_bytes = fill_padding;
increase_used(partition, fill_padding);
}
_membership[int(partition)].clear_bit(idx);
decrease_region_counts(partition, 1);
shrink_interval_if_boundary_modified(partition, idx);
// This region is fully used, whether or not top() equals end(). It
// is retired and no more memory will be allocated from within it.
return waste_bytes;
}
void ShenandoahRegionPartitions::unretire_to_partition(ShenandoahHeapRegion* r, ShenandoahFreeSetPartitionId which_partition) {
shenandoah_assert_heaplocked();
make_free(r->index(), which_partition, r->free());
}
// The caller is responsible for increasing capacity and available and used in which_partition, and decreasing the
// same quantities for the original partition
void ShenandoahRegionPartitions::make_free(idx_t idx, ShenandoahFreeSetPartitionId which_partition, size_t available) {
shenandoah_assert_heaplocked();
assert (idx < _max, "index is sane: %zu < %zu", idx, _max);
assert (membership(idx) == ShenandoahFreeSetPartitionId::NotFree, "Cannot make free if already free");
assert (which_partition < NumPartitions, "selected free partition must be valid");
assert (available <= _region_size_bytes, "Available cannot exceed region size");
_membership[int(which_partition)].set_bit(idx);
expand_interval_if_boundary_modified(which_partition, idx, available);
}
bool ShenandoahRegionPartitions::is_mutator_partition(ShenandoahFreeSetPartitionId p) {
return (p == ShenandoahFreeSetPartitionId::Mutator);
}
bool ShenandoahRegionPartitions::is_young_collector_partition(ShenandoahFreeSetPartitionId p) {
return (p == ShenandoahFreeSetPartitionId::Collector);
}
bool ShenandoahRegionPartitions::is_old_collector_partition(ShenandoahFreeSetPartitionId p) {
return (p == ShenandoahFreeSetPartitionId::OldCollector);
}
bool ShenandoahRegionPartitions::available_implies_empty(size_t available_in_region) {
return (available_in_region == _region_size_bytes);
}
// Do not adjust capacities, available, or used. Return used delta.
size_t ShenandoahRegionPartitions::
move_from_partition_to_partition_with_deferred_accounting(idx_t idx, ShenandoahFreeSetPartitionId orig_partition,
ShenandoahFreeSetPartitionId new_partition, size_t available) {
ShenandoahHeapRegion* r = ShenandoahHeap::heap()->get_region(idx);
shenandoah_assert_heaplocked();
assert (idx < _max, "index is sane: %zu < %zu", idx, _max);
assert (orig_partition < NumPartitions, "Original partition must be valid");
assert (new_partition < NumPartitions, "New partition must be valid");
assert (available <= _region_size_bytes, "Available cannot exceed region size");
assert (_membership[int(orig_partition)].is_set(idx), "Cannot move from partition unless in partition");
assert ((r != nullptr) && ((r->is_trash() && (available == _region_size_bytes)) ||
(r->used() + available == _region_size_bytes)),
"Used: %zu + available: %zu should equal region size: %zu",
ShenandoahHeap::heap()->get_region(idx)->used(), available, _region_size_bytes);
// Expected transitions:
// During rebuild: Mutator => Collector
// Mutator empty => Collector
// Mutator empty => OldCollector
// During flip_to_gc: Mutator empty => Collector
// Mutator empty => OldCollector
// At start of update refs: Collector => Mutator
// OldCollector Empty => Mutator
assert ((is_mutator_partition(orig_partition) && is_young_collector_partition(new_partition)) ||
(is_mutator_partition(orig_partition) &&
available_implies_empty(available) && is_old_collector_partition(new_partition)) ||
(is_young_collector_partition(orig_partition) && is_mutator_partition(new_partition)) ||
(is_old_collector_partition(orig_partition)
&& available_implies_empty(available) && is_mutator_partition(new_partition)),
"Unexpected movement between partitions, available: %zu, _region_size_bytes: %zu"
", orig_partition: %s, new_partition: %s",
available, _region_size_bytes, partition_name(orig_partition), partition_name(new_partition));
size_t used = _region_size_bytes - available;
assert (_used[int(orig_partition)] >= used,
"Orig partition used: %zu must exceed moved used: %zu within region %zd",
_used[int(orig_partition)], used, idx);
_membership[int(orig_partition)].clear_bit(idx);
_membership[int(new_partition)].set_bit(idx);
return used;
}
void ShenandoahRegionPartitions::move_from_partition_to_partition(idx_t idx, ShenandoahFreeSetPartitionId orig_partition,
ShenandoahFreeSetPartitionId new_partition, size_t available) {
size_t used = move_from_partition_to_partition_with_deferred_accounting(idx, orig_partition, new_partition, available);
// We decreased used, which increases available, but then we decrease available by full region size below
decrease_used(orig_partition, used);
_region_counts[int(orig_partition)]--;
_capacity[int(orig_partition)] -= _region_size_bytes;
_available[int(orig_partition)] -= _region_size_bytes;
shrink_interval_if_boundary_modified(orig_partition, idx);
_capacity[int(new_partition)] += _region_size_bytes;
_available[int(new_partition)] += _region_size_bytes;
_region_counts[int(new_partition)]++;
// We increased availableby full region size above, but decrease it by used within this region now.
increase_used(new_partition, used);
expand_interval_if_boundary_modified(new_partition, idx, available);
if (available == _region_size_bytes) {
_empty_region_counts[int(orig_partition)]--;
_empty_region_counts[int(new_partition)]++;
}
}
const char* ShenandoahRegionPartitions::partition_membership_name(idx_t idx) const {
return partition_name(membership(idx));
}
#ifdef ASSERT
inline bool ShenandoahRegionPartitions::partition_id_matches(idx_t idx, ShenandoahFreeSetPartitionId test_partition) const {
assert (idx < _max, "index is sane: %zu < %zu", idx, _max);
assert (test_partition < ShenandoahFreeSetPartitionId::NotFree, "must be a valid partition");
return membership(idx) == test_partition;
}
#endif
inline bool ShenandoahRegionPartitions::is_empty(ShenandoahFreeSetPartitionId which_partition) const {
assert (which_partition < NumPartitions, "selected free partition must be valid");
return (leftmost(which_partition) > rightmost(which_partition));
}
inline idx_t ShenandoahRegionPartitions::find_index_of_next_available_region(
ShenandoahFreeSetPartitionId which_partition, idx_t start_index) const {
idx_t rightmost_idx = rightmost(which_partition);
idx_t leftmost_idx = leftmost(which_partition);
if ((rightmost_idx < leftmost_idx) || (start_index > rightmost_idx)) return _max;
if (start_index < leftmost_idx) {
start_index = leftmost_idx;
}
idx_t result = _membership[int(which_partition)].find_first_set_bit(start_index, rightmost_idx + 1);
if (result > rightmost_idx) {
result = _max;
}
assert (result >= start_index, "Requires progress");
return result;
}
inline idx_t ShenandoahRegionPartitions::find_index_of_previous_available_region(
ShenandoahFreeSetPartitionId which_partition, idx_t last_index) const {
idx_t rightmost_idx = rightmost(which_partition);
idx_t leftmost_idx = leftmost(which_partition);
// if (leftmost_idx == max) then (last_index < leftmost_idx)
if (last_index < leftmost_idx) return -1;
if (last_index > rightmost_idx) {
last_index = rightmost_idx;
}
idx_t result = _membership[int(which_partition)].find_last_set_bit(-1, last_index);
if (result < leftmost_idx) {
result = -1;
}
assert (result <= last_index, "Requires progress");
return result;
}
inline idx_t ShenandoahRegionPartitions::find_index_of_next_available_cluster_of_regions(
ShenandoahFreeSetPartitionId which_partition, idx_t start_index, size_t cluster_size) const {
idx_t rightmost_idx = rightmost(which_partition);
idx_t leftmost_idx = leftmost(which_partition);
if ((rightmost_idx < leftmost_idx) || (start_index > rightmost_idx)) return _max;
idx_t result =
_membership[int(which_partition)].find_first_consecutive_set_bits(start_index, rightmost_idx + 1, cluster_size);
if (result > rightmost_idx) {
result = _max;
}
assert (result >= start_index, "Requires progress");
return result;
}
inline idx_t ShenandoahRegionPartitions::find_index_of_previous_available_cluster_of_regions(
ShenandoahFreeSetPartitionId which_partition, idx_t last_index, size_t cluster_size) const {
idx_t leftmost_idx = leftmost(which_partition);
// if (leftmost_idx == max) then (last_index < leftmost_idx)
if (last_index < leftmost_idx) return -1;
idx_t result = _membership[int(which_partition)].find_last_consecutive_set_bits(leftmost_idx - 1, last_index, cluster_size);
if (result <= leftmost_idx) {
result = -1;
}
assert (result <= last_index, "Requires progress");
return result;
}
idx_t ShenandoahRegionPartitions::leftmost_empty(ShenandoahFreeSetPartitionId which_partition) {
assert (which_partition < NumPartitions, "selected free partition must be valid");
idx_t max_regions = _max;
if (_leftmosts_empty[int(which_partition)] == _max) {
return _max;
}
for (idx_t idx = find_index_of_next_available_region(which_partition, _leftmosts_empty[int(which_partition)]);
idx < max_regions; ) {
assert(in_free_set(which_partition, idx), "Boundaries or find_last_set_bit failed: %zd", idx);
if (_free_set->alloc_capacity(idx) == _region_size_bytes) {
_leftmosts_empty[int(which_partition)] = idx;
return idx;
}
idx = find_index_of_next_available_region(which_partition, idx + 1);
}
_leftmosts_empty[int(which_partition)] = _max;
_rightmosts_empty[int(which_partition)] = -1;
return _max;
}
idx_t ShenandoahRegionPartitions::rightmost_empty(ShenandoahFreeSetPartitionId which_partition) {
assert (which_partition < NumPartitions, "selected free partition must be valid");
if (_rightmosts_empty[int(which_partition)] < 0) {
return -1;
}
for (idx_t idx = find_index_of_previous_available_region(which_partition, _rightmosts_empty[int(which_partition)]);
idx >= 0; ) {
assert(in_free_set(which_partition, idx), "Boundaries or find_last_set_bit failed: %zd", idx);
if (_free_set->alloc_capacity(idx) == _region_size_bytes) {
_rightmosts_empty[int(which_partition)] = idx;
return idx;
}
idx = find_index_of_previous_available_region(which_partition, idx - 1);
}
_leftmosts_empty[int(which_partition)] = _max;
_rightmosts_empty[int(which_partition)] = -1;
return -1;
}
#ifdef ASSERT
void ShenandoahRegionPartitions::assert_bounds() {
size_t capacities[UIntNumPartitions];
size_t used[UIntNumPartitions];
size_t regions[UIntNumPartitions];
size_t humongous_waste[UIntNumPartitions];
// We don't know whether young retired regions belonged to Mutator or Collector before they were retired.
// We just tally the total, and divide it to make matches work if possible.
size_t young_retired_regions = 0;
size_t young_retired_used = 0;
size_t young_retired_capacity = 0;
size_t young_humongous_waste = 0;
idx_t leftmosts[UIntNumPartitions];
idx_t rightmosts[UIntNumPartitions];
idx_t empty_leftmosts[UIntNumPartitions];
idx_t empty_rightmosts[UIntNumPartitions];
for (uint i = 0; i < UIntNumPartitions; i++) {
leftmosts[i] = _max;
empty_leftmosts[i] = _max;
rightmosts[i] = -1;
empty_rightmosts[i] = -1;
capacities[i] = 0;
used[i] = 0;
regions[i] = 0;
humongous_waste[i] = 0;
}
for (idx_t i = 0; i < _max; i++) {
ShenandoahFreeSetPartitionId partition = membership(i);
size_t capacity = _free_set->alloc_capacity(i);
switch (partition) {
case ShenandoahFreeSetPartitionId::NotFree:
{
assert(capacity != _region_size_bytes, "Should not be retired if empty");
ShenandoahHeapRegion* r = ShenandoahHeap::heap()->get_region(i);
if (r->is_humongous()) {
if (r->is_old()) {
regions[int(ShenandoahFreeSetPartitionId::OldCollector)]++;
used[int(ShenandoahFreeSetPartitionId::OldCollector)] += _region_size_bytes;
capacities[int(ShenandoahFreeSetPartitionId::OldCollector)] += _region_size_bytes;
humongous_waste[int(ShenandoahFreeSetPartitionId::OldCollector)] += capacity;
} else {
assert(r->is_young(), "Must be young if not old");
young_retired_regions++;
// Count entire region as used even if there is some waste.
young_retired_used += _region_size_bytes;
young_retired_capacity += _region_size_bytes;
young_humongous_waste += capacity;
}
} else {
assert(r->is_cset() || (capacity < PLAB::min_size() * HeapWordSize),
"Expect retired remnant size to be smaller than min plab size");
// This region has been retired already or it is in the cset. In either case, we set capacity to zero
// so that the entire region will be counted as used. We count young cset regions as "retired".
capacity = 0;
if (r->is_old()) {
regions[int(ShenandoahFreeSetPartitionId::OldCollector)]++;
used[int(ShenandoahFreeSetPartitionId::OldCollector)] += _region_size_bytes - capacity;
capacities[int(ShenandoahFreeSetPartitionId::OldCollector)] += _region_size_bytes;
} else {
assert(r->is_young(), "Must be young if not old");
young_retired_regions++;
young_retired_used += _region_size_bytes - capacity;
young_retired_capacity += _region_size_bytes;
}
}
}
break;
case ShenandoahFreeSetPartitionId::Mutator:
case ShenandoahFreeSetPartitionId::Collector:
case ShenandoahFreeSetPartitionId::OldCollector:
{
ShenandoahHeapRegion* r = ShenandoahHeap::heap()->get_region(i);
assert(capacity > 0, "free regions must have allocation capacity");
bool is_empty = (capacity == _region_size_bytes);
regions[int(partition)]++;
used[int(partition)] += _region_size_bytes - capacity;
capacities[int(partition)] += _region_size_bytes;
if (i < leftmosts[int(partition)]) {
leftmosts[int(partition)] = i;
}
if (is_empty && (i < empty_leftmosts[int(partition)])) {
empty_leftmosts[int(partition)] = i;
}
if (i > rightmosts[int(partition)]) {
rightmosts[int(partition)] = i;
}
if (is_empty && (i > empty_rightmosts[int(partition)])) {
empty_rightmosts[int(partition)] = i;
}
break;
}
default:
ShouldNotReachHere();
}
}
// Performance invariants. Failing these would not break the free partition, but performance would suffer.
assert (leftmost(ShenandoahFreeSetPartitionId::Mutator) <= _max,
"leftmost in bounds: %zd < %zd", leftmost(ShenandoahFreeSetPartitionId::Mutator), _max);
assert (rightmost(ShenandoahFreeSetPartitionId::Mutator) < _max,
"rightmost in bounds: %zd < %zd", rightmost(ShenandoahFreeSetPartitionId::Mutator), _max);
assert (leftmost(ShenandoahFreeSetPartitionId::Mutator) == _max
|| partition_id_matches(leftmost(ShenandoahFreeSetPartitionId::Mutator), ShenandoahFreeSetPartitionId::Mutator),
"leftmost region should be free: %zd", leftmost(ShenandoahFreeSetPartitionId::Mutator));
assert (leftmost(ShenandoahFreeSetPartitionId::Mutator) == _max
|| partition_id_matches(rightmost(ShenandoahFreeSetPartitionId::Mutator), ShenandoahFreeSetPartitionId::Mutator),
"rightmost region should be free: %zd", rightmost(ShenandoahFreeSetPartitionId::Mutator));
// If Mutator partition is empty, leftmosts will both equal max, rightmosts will both equal zero.
// Likewise for empty region partitions.
idx_t beg_off = leftmosts[int(ShenandoahFreeSetPartitionId::Mutator)];
idx_t end_off = rightmosts[int(ShenandoahFreeSetPartitionId::Mutator)];
assert (beg_off >= leftmost(ShenandoahFreeSetPartitionId::Mutator),
"Mutator free region before the leftmost: %zd, bound %zd",
beg_off, leftmost(ShenandoahFreeSetPartitionId::Mutator));
assert (end_off <= rightmost(ShenandoahFreeSetPartitionId::Mutator),
"Mutator free region past the rightmost: %zd, bound %zd",
end_off, rightmost(ShenandoahFreeSetPartitionId::Mutator));
beg_off = empty_leftmosts[int(ShenandoahFreeSetPartitionId::Mutator)];
end_off = empty_rightmosts[int(ShenandoahFreeSetPartitionId::Mutator)];
assert (beg_off >= _leftmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)],
"free empty region (%zd) before the leftmost bound %zd",
beg_off, _leftmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)]);
assert (end_off <= _rightmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)],
"free empty region (%zd) past the rightmost bound %zd",
end_off, _rightmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)]);
// Performance invariants. Failing these would not break the free partition, but performance would suffer.
assert (leftmost(ShenandoahFreeSetPartitionId::Collector) <= _max, "leftmost in bounds: %zd < %zd",
leftmost(ShenandoahFreeSetPartitionId::Collector), _max);
assert (rightmost(ShenandoahFreeSetPartitionId::Collector) < _max, "rightmost in bounds: %zd < %zd",
rightmost(ShenandoahFreeSetPartitionId::Collector), _max);
assert (leftmost(ShenandoahFreeSetPartitionId::Collector) == _max
|| partition_id_matches(leftmost(ShenandoahFreeSetPartitionId::Collector), ShenandoahFreeSetPartitionId::Collector),
"Collector leftmost region should be free: %zd", leftmost(ShenandoahFreeSetPartitionId::Collector));
assert (leftmost(ShenandoahFreeSetPartitionId::Collector) == _max
|| partition_id_matches(rightmost(ShenandoahFreeSetPartitionId::Collector), ShenandoahFreeSetPartitionId::Collector),
"Collector rightmost region should be free: %zd", rightmost(ShenandoahFreeSetPartitionId::Collector));
// If Collector partition is empty, leftmosts will both equal max, rightmosts will both equal zero.
// Likewise for empty region partitions.
beg_off = leftmosts[int(ShenandoahFreeSetPartitionId::Collector)];
end_off = rightmosts[int(ShenandoahFreeSetPartitionId::Collector)];
assert (beg_off >= leftmost(ShenandoahFreeSetPartitionId::Collector),
"Collector free region before the leftmost: %zd, bound %zd",
beg_off, leftmost(ShenandoahFreeSetPartitionId::Collector));
assert (end_off <= rightmost(ShenandoahFreeSetPartitionId::Collector),
"Collector free region past the rightmost: %zd, bound %zd",
end_off, rightmost(ShenandoahFreeSetPartitionId::Collector));
beg_off = empty_leftmosts[int(ShenandoahFreeSetPartitionId::Collector)];
end_off = empty_rightmosts[int(ShenandoahFreeSetPartitionId::Collector)];
assert (beg_off >= _leftmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)],
"Collector free empty region before the leftmost: %zd, bound %zd",
beg_off, _leftmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)]);
assert (end_off <= _rightmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)],
"Collector free empty region past the rightmost: %zd, bound %zd",
end_off, _rightmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)]);
// Performance invariants. Failing these would not break the free partition, but performance would suffer.
assert (leftmost(ShenandoahFreeSetPartitionId::OldCollector) <= _max, "OldCollector leftmost in bounds: %zd < %zd",
leftmost(ShenandoahFreeSetPartitionId::OldCollector), _max);
assert (rightmost(ShenandoahFreeSetPartitionId::OldCollector) < _max, "OldCollector rightmost in bounds: %zd < %zd",
rightmost(ShenandoahFreeSetPartitionId::OldCollector), _max);
assert (leftmost(ShenandoahFreeSetPartitionId::OldCollector) == _max
|| partition_id_matches(leftmost(ShenandoahFreeSetPartitionId::OldCollector),
ShenandoahFreeSetPartitionId::OldCollector),
"OldCollector leftmost region should be free: %zd", leftmost(ShenandoahFreeSetPartitionId::OldCollector));
assert (leftmost(ShenandoahFreeSetPartitionId::OldCollector) == _max
|| partition_id_matches(rightmost(ShenandoahFreeSetPartitionId::OldCollector),
ShenandoahFreeSetPartitionId::OldCollector),
"OldCollector rightmost region should be free: %zd", rightmost(ShenandoahFreeSetPartitionId::OldCollector));
// Concurrent recycling of trash recycles a region (changing its state from is_trash to is_empty without the heap lock),
// If OldCollector partition is empty, leftmosts will both equal max, rightmosts will both equal zero.
// Likewise for empty region partitions.
beg_off = leftmosts[int(ShenandoahFreeSetPartitionId::OldCollector)];
end_off = rightmosts[int(ShenandoahFreeSetPartitionId::OldCollector)];
assert (beg_off >= leftmost(ShenandoahFreeSetPartitionId::OldCollector), "free regions before the leftmost: %zd, bound %zd",
beg_off, leftmost(ShenandoahFreeSetPartitionId::OldCollector));
assert (end_off <= rightmost(ShenandoahFreeSetPartitionId::OldCollector), "free regions past the rightmost: %zd, bound %zd",
end_off, rightmost(ShenandoahFreeSetPartitionId::OldCollector));
beg_off = empty_leftmosts[int(ShenandoahFreeSetPartitionId::OldCollector)];
end_off = empty_rightmosts[int(ShenandoahFreeSetPartitionId::OldCollector)];
assert (beg_off >= _leftmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)],
"free empty region (%zd) before the leftmost bound %zd, region %s trash",
beg_off, _leftmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)],
((beg_off >= _max)? "out of bounds is not":
(ShenandoahHeap::heap()->get_region(_leftmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)])->is_trash()?
"is": "is not")));
assert (end_off <= _rightmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)],
"free empty region (%zd) past the rightmost bound %zd, region %s trash",
end_off, _rightmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)],
((end_off < 0)? "out of bounds is not" :
(ShenandoahHeap::heap()->get_region(_rightmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)])->is_trash()?
"is": "is not")));
// young_retired_regions need to be added to either Mutator or Collector partitions, 100% used.
// Give enough of young_retired_regions, young_retired_capacity, young_retired_user
// to the Mutator partition to top it off so that it matches the running totals.
//
// Give any remnants to the Collector partition. After topping off the Collector partition, its values
// should also match running totals.
assert(young_retired_regions * _region_size_bytes == young_retired_capacity, "sanity");
assert(young_retired_capacity == young_retired_used, "sanity");
assert(capacities[int(ShenandoahFreeSetPartitionId::OldCollector)]
== _capacity[int(ShenandoahFreeSetPartitionId::OldCollector)], "Old collector capacities must match (%zu != %zu)",
capacities[int(ShenandoahFreeSetPartitionId::OldCollector)],
_capacity[int(ShenandoahFreeSetPartitionId::OldCollector)]);
assert(used[int(ShenandoahFreeSetPartitionId::OldCollector)]
== _used[int(ShenandoahFreeSetPartitionId::OldCollector)], "Old collector used must match");
assert(regions[int(ShenandoahFreeSetPartitionId::OldCollector)]
== _capacity[int(ShenandoahFreeSetPartitionId::OldCollector)] / _region_size_bytes, "Old collector regions must match");
assert(_capacity[int(ShenandoahFreeSetPartitionId::OldCollector)]
>= _used[int(ShenandoahFreeSetPartitionId::OldCollector)], "Old Collector capacity must be >= used");
assert(_available[int(ShenandoahFreeSetPartitionId::OldCollector)] ==
(_capacity[int(ShenandoahFreeSetPartitionId::OldCollector)] - _used[int(ShenandoahFreeSetPartitionId::OldCollector)]),
"Old Collector available must equal capacity minus used");
assert(_humongous_waste[int(ShenandoahFreeSetPartitionId::OldCollector)] ==
humongous_waste[int(ShenandoahFreeSetPartitionId::OldCollector)], "Old Collector humongous waste must match");
assert(_capacity[int(ShenandoahFreeSetPartitionId::Mutator)] >= capacities[int(ShenandoahFreeSetPartitionId::Mutator)],
"Capacity total must be >= counted tally");
size_t mutator_capacity_shortfall =
_capacity[int(ShenandoahFreeSetPartitionId::Mutator)] - capacities[int(ShenandoahFreeSetPartitionId::Mutator)];
assert(mutator_capacity_shortfall <= young_retired_capacity, "sanity");
capacities[int(ShenandoahFreeSetPartitionId::Mutator)] += mutator_capacity_shortfall;
young_retired_capacity -= mutator_capacity_shortfall;
capacities[int(ShenandoahFreeSetPartitionId::Collector)] += young_retired_capacity;
assert(_used[int(ShenandoahFreeSetPartitionId::Mutator)] >= used[int(ShenandoahFreeSetPartitionId::Mutator)],
"Used total must be >= counted tally");
size_t mutator_used_shortfall =
_used[int(ShenandoahFreeSetPartitionId::Mutator)] - used[int(ShenandoahFreeSetPartitionId::Mutator)];
assert(mutator_used_shortfall <= young_retired_used, "sanity");
used[int(ShenandoahFreeSetPartitionId::Mutator)] += mutator_used_shortfall;
young_retired_used -= mutator_used_shortfall;
used[int(ShenandoahFreeSetPartitionId::Collector)] += young_retired_used;
assert(_capacity[int(ShenandoahFreeSetPartitionId::Mutator)] / _region_size_bytes
>= regions[int(ShenandoahFreeSetPartitionId::Mutator)], "Region total must be >= counted tally");
size_t mutator_regions_shortfall = (_capacity[int(ShenandoahFreeSetPartitionId::Mutator)] / _region_size_bytes
- regions[int(ShenandoahFreeSetPartitionId::Mutator)]);
assert(mutator_regions_shortfall <= young_retired_regions, "sanity");
regions[int(ShenandoahFreeSetPartitionId::Mutator)] += mutator_regions_shortfall;
young_retired_regions -= mutator_regions_shortfall;
regions[int(ShenandoahFreeSetPartitionId::Collector)] += young_retired_regions;
assert(capacities[int(ShenandoahFreeSetPartitionId::Collector)] == _capacity[int(ShenandoahFreeSetPartitionId::Collector)],
"Collector capacities must match");
assert(used[int(ShenandoahFreeSetPartitionId::Collector)] == _used[int(ShenandoahFreeSetPartitionId::Collector)],
"Collector used must match");
assert(regions[int(ShenandoahFreeSetPartitionId::Collector)]
== _capacity[int(ShenandoahFreeSetPartitionId::Collector)] / _region_size_bytes, "Collector regions must match");
assert(_capacity[int(ShenandoahFreeSetPartitionId::Collector)] >= _used[int(ShenandoahFreeSetPartitionId::Collector)],
"Collector Capacity must be >= used");
assert(_available[int(ShenandoahFreeSetPartitionId::Collector)] ==
(_capacity[int(ShenandoahFreeSetPartitionId::Collector)] - _used[int(ShenandoahFreeSetPartitionId::Collector)]),
"Collector Available must equal capacity minus used");
assert(capacities[int(ShenandoahFreeSetPartitionId::Mutator)] == _capacity[int(ShenandoahFreeSetPartitionId::Mutator)],
"Mutator capacities must match");
assert(used[int(ShenandoahFreeSetPartitionId::Mutator)] == _used[int(ShenandoahFreeSetPartitionId::Mutator)],
"Mutator used must match");
assert(regions[int(ShenandoahFreeSetPartitionId::Mutator)]
== _capacity[int(ShenandoahFreeSetPartitionId::Mutator)] / _region_size_bytes, "Mutator regions must match");
assert(_capacity[int(ShenandoahFreeSetPartitionId::Mutator)] >= _used[int(ShenandoahFreeSetPartitionId::Mutator)],
"Mutator capacity must be >= used");
assert(_available[int(ShenandoahFreeSetPartitionId::Mutator)] ==
(_capacity[int(ShenandoahFreeSetPartitionId::Mutator)] - _used[int(ShenandoahFreeSetPartitionId::Mutator)]),
"Mutator available must equal capacity minus used");
assert(_humongous_waste[int(ShenandoahFreeSetPartitionId::Mutator)] == young_humongous_waste,
"Mutator humongous waste must match");
}
#endif
ShenandoahFreeSet::ShenandoahFreeSet(ShenandoahHeap* heap, size_t max_regions) :
_heap(heap),
_partitions(max_regions, this),
_total_bytes_previously_allocated(0),
_mutator_bytes_at_last_sample(0),
_total_humongous_waste(0),
_alloc_bias_weight(0),
_total_young_used(0),
_total_old_used(0),
_total_global_used(0),
_young_affiliated_regions(0),
_old_affiliated_regions(0),
_global_affiliated_regions(0),
_young_unaffiliated_regions(0),
_global_unaffiliated_regions(0),
_total_young_regions(0),
_total_global_regions(0),
_mutator_bytes_allocated_since_gc_start(0)
{
clear_internal();
}
void ShenandoahFreeSet::move_unaffiliated_regions_from_collector_to_old_collector(ssize_t count) {
shenandoah_assert_heaplocked();
size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
size_t old_capacity = _partitions.get_capacity(ShenandoahFreeSetPartitionId::OldCollector);
size_t collector_capacity = _partitions.get_capacity(ShenandoahFreeSetPartitionId::Collector);
if (count > 0) {
size_t ucount = count;
size_t bytes_moved = ucount * region_size_bytes;
assert(collector_capacity >= bytes_moved, "Cannot transfer");
assert(_partitions.get_empty_region_counts(ShenandoahFreeSetPartitionId::Collector) >= ucount,
"Cannot transfer %zu of %zu", ucount, _partitions.get_empty_region_counts(ShenandoahFreeSetPartitionId::Collector));
_partitions.decrease_empty_region_counts(ShenandoahFreeSetPartitionId::Collector, ucount);
_partitions.set_capacity_of(ShenandoahFreeSetPartitionId::Collector, collector_capacity - bytes_moved);
_partitions.set_capacity_of(ShenandoahFreeSetPartitionId::OldCollector, old_capacity + bytes_moved);
_partitions.increase_empty_region_counts(ShenandoahFreeSetPartitionId::OldCollector, ucount);
} else if (count < 0) {
size_t ucount = -count;
size_t bytes_moved = ucount * region_size_bytes;
assert(old_capacity >= bytes_moved, "Cannot transfer");
assert(_partitions.get_empty_region_counts(ShenandoahFreeSetPartitionId::OldCollector) >= ucount,
"Cannot transfer %zu of %zu", ucount, _partitions.get_empty_region_counts(ShenandoahFreeSetPartitionId::OldCollector));
_partitions.decrease_empty_region_counts(ShenandoahFreeSetPartitionId::OldCollector, ucount);
_partitions.set_capacity_of(ShenandoahFreeSetPartitionId::OldCollector, old_capacity - bytes_moved);
_partitions.set_capacity_of(ShenandoahFreeSetPartitionId::Collector, collector_capacity + bytes_moved);
_partitions.increase_empty_region_counts(ShenandoahFreeSetPartitionId::Collector, ucount);
}
// else, do nothing
}
// was pip_pad_bytes
void ShenandoahFreeSet::add_promoted_in_place_region_to_old_collector(ShenandoahHeapRegion* region) {
shenandoah_assert_heaplocked();
size_t plab_min_size_in_bytes = ShenandoahGenerationalHeap::heap()->plab_min_size() * HeapWordSize;
size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
size_t available_in_region = alloc_capacity(region);
size_t region_index = region->index();
ShenandoahFreeSetPartitionId p = _partitions.membership(region_index);
assert(_partitions.membership(region_index) == ShenandoahFreeSetPartitionId::NotFree,
"Regions promoted in place should have been excluded from Mutator partition");
// If region had been retired, its end-of-region alignment pad had been counted as used within the Mutator partition
size_t used_while_awaiting_pip = region_size_bytes;
size_t used_after_pip = region_size_bytes;
if (available_in_region >= plab_min_size_in_bytes) {
used_after_pip -= available_in_region;
} else {
if (available_in_region >= ShenandoahHeap::min_fill_size() * HeapWordSize) {
size_t fill_words = available_in_region / HeapWordSize;
ShenandoahHeap::heap()->old_generation()->card_scan()->register_object(region->top());
region->allocate_fill(fill_words);
}
available_in_region = 0;
}
assert(p == ShenandoahFreeSetPartitionId::NotFree, "pip region must be NotFree");
assert(region->is_young(), "pip region must be young");
// Though this region may have been promoted in place from the Collector region, its usage is now accounted within
// the Mutator partition.
_partitions.decrease_used(ShenandoahFreeSetPartitionId::Mutator, used_while_awaiting_pip);
// decrease capacity adjusts available
_partitions.decrease_capacity(ShenandoahFreeSetPartitionId::Mutator, region_size_bytes);
_partitions.increase_capacity(ShenandoahFreeSetPartitionId::OldCollector, region_size_bytes);
_partitions.increase_used(ShenandoahFreeSetPartitionId::OldCollector, used_after_pip);
region->set_affiliation(ShenandoahAffiliation::OLD_GENERATION);
if (available_in_region > 0) {
assert(available_in_region >= plab_min_size_in_bytes, "enforced above");
_partitions.increase_region_counts(ShenandoahFreeSetPartitionId::OldCollector, 1);
// make_free() adjusts bounds for OldCollector partition
_partitions.make_free(region_index, ShenandoahFreeSetPartitionId::OldCollector, available_in_region);
_heap->old_generation()->augment_promoted_reserve(available_in_region);
assert(available_in_region != region_size_bytes, "Nothing to promote in place");
}
// else, leave this region as NotFree
recompute_total_used</* UsedByMutatorChanged */ true,
/* UsedByCollectorChanged */ false, /* UsedByOldCollectorChanged */ true>();
// Conservatively, assume that pip regions came from both Mutator and Collector
recompute_total_affiliated</* MutatorEmptiesChanged */ false, /* CollectorEmptiesChanged */ false,
/* OldCollectorEmptiesChanged */ false, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ true, /* OldCollectorSizeChanged */ true,
/* AffiliatedChangesAreYoungNeutral */ false, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ true>();
_partitions.assert_bounds();
}
template<typename Iter>
HeapWord* ShenandoahFreeSet::allocate_with_affiliation(Iter& iterator,
ShenandoahAffiliation affiliation,
ShenandoahAllocRequest& req,
bool& in_new_region) {
assert(affiliation != ShenandoahAffiliation::FREE, "Must not");
ShenandoahHeapRegion* free_region = nullptr;
for (idx_t idx = iterator.current(); iterator.has_next(); idx = iterator.next()) {
ShenandoahHeapRegion* r = _heap->get_region(idx);
if (r->affiliation() == affiliation) {
HeapWord* result = try_allocate_in(r, req, in_new_region);
if (result != nullptr) {
return result;
}
} else if (free_region == nullptr && r->affiliation() == FREE) {
free_region = r;
}
}
// Failed to allocate within any affiliated region, try the first free region in the partition.
if (free_region != nullptr) {
HeapWord* result = try_allocate_in(free_region, req, in_new_region);
assert(result != nullptr, "Allocate in free region in the partition always succeed.");
return result;
}
log_debug(gc, free)("Could not allocate collector region with affiliation: %s for request " PTR_FORMAT,
shenandoah_affiliation_name(affiliation), p2i(&req));
return nullptr;
}
HeapWord* ShenandoahFreeSet::allocate_single(ShenandoahAllocRequest& req, bool& in_new_region) {
shenandoah_assert_heaplocked();
// Scan the bitmap looking for a first fit.
//
// Leftmost and rightmost bounds provide enough caching to walk bitmap efficiently. Normally,
// we would find the region to allocate at right away.
//
// Allocations are biased: GC allocations are taken from the high end of the heap. Regular (and TLAB)
// mutator allocations are taken from the middle of heap, below the memory reserved for Collector.
// Humongous mutator allocations are taken from the bottom of the heap.
//
// Free set maintains mutator and collector partitions. Normally, each allocates only from its partition,
// except in special cases when the collector steals regions from the mutator partition.
// Overwrite with non-zero (non-null) values only if necessary for allocation bookkeeping.
if (req.is_mutator_alloc()) {
return allocate_for_mutator(req, in_new_region);
} else {
return allocate_for_collector(req, in_new_region);
}
}
HeapWord* ShenandoahFreeSet::allocate_for_mutator(ShenandoahAllocRequest &req, bool &in_new_region) {
update_allocation_bias();
if (_partitions.is_empty(ShenandoahFreeSetPartitionId::Mutator)) {
// There is no recovery. Mutator does not touch collector view at all.
return nullptr;
}
// Try to allocate in the mutator view
if (_partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::Mutator)) {
// Allocate from low to high memory. This keeps the range of fully empty regions more tightly packed.
// Note that the most recently allocated regions tend not to be evacuated in a given GC cycle. So this
// tends to accumulate "fragmented" uncollected regions in high memory.
ShenandoahLeftRightIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
return allocate_from_regions(iterator, req, in_new_region);
}
// Allocate from high to low memory. This preserves low memory for humongous allocations.
ShenandoahRightLeftIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
return allocate_from_regions(iterator, req, in_new_region);
}
void ShenandoahFreeSet::update_allocation_bias() {
if (_alloc_bias_weight-- <= 0) {
// We have observed that regions not collected in previous GC cycle tend to congregate at one end or the other
// of the heap. Typically, these are the more recently engaged regions and the objects in these regions have not
// yet had a chance to die (and/or are treated as floating garbage). If we use the same allocation bias on each
// GC pass, these "most recently" engaged regions for GC pass N will also be the "most recently" engaged regions
// for GC pass N+1, and the relatively large amount of live data and/or floating garbage introduced
// during the most recent GC pass may once again prevent the region from being collected. We have found that
// alternating the allocation behavior between GC passes improves evacuation performance by 3-7% on certain
// benchmarks. In the best case, this has the effect of consuming these partially consumed regions before
// the start of the next mark cycle so all of their garbage can be efficiently reclaimed.
//
// First, finish consuming regions that are already partially consumed so as to more tightly limit ranges of
// available regions. Other potential benefits:
// 1. Eventual collection set has fewer regions because we have packed newly allocated objects into fewer regions
// 2. We preserve the "empty" regions longer into the GC cycle, reducing likelihood of allocation failures
// late in the GC cycle.
idx_t non_empty_on_left = (_partitions.leftmost_empty(ShenandoahFreeSetPartitionId::Mutator)
- _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator));
idx_t non_empty_on_right = (_partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator)
- _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::Mutator));
_partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::Mutator, (non_empty_on_right < non_empty_on_left));
_alloc_bias_weight = INITIAL_ALLOC_BIAS_WEIGHT;
}
}
template<typename Iter>
HeapWord* ShenandoahFreeSet::allocate_from_regions(Iter& iterator, ShenandoahAllocRequest &req, bool &in_new_region) {
for (idx_t idx = iterator.current(); iterator.has_next(); idx = iterator.next()) {
ShenandoahHeapRegion* r = _heap->get_region(idx);
size_t min_size = req.is_lab_alloc() ? req.min_size() : req.size();
if (alloc_capacity(r) >= min_size * HeapWordSize) {
HeapWord* result = try_allocate_in(r, req, in_new_region);
if (result != nullptr) {
return result;
}
}
}
return nullptr;
}
HeapWord* ShenandoahFreeSet::allocate_for_collector(ShenandoahAllocRequest &req, bool &in_new_region) {
shenandoah_assert_heaplocked();
ShenandoahFreeSetPartitionId which_partition = req.is_old()? ShenandoahFreeSetPartitionId::OldCollector: ShenandoahFreeSetPartitionId::Collector;
HeapWord* result = nullptr;
if (_partitions.alloc_from_left_bias(which_partition)) {
ShenandoahLeftRightIterator iterator(&_partitions, which_partition);
result = allocate_with_affiliation(iterator, req.affiliation(), req, in_new_region);
} else {
ShenandoahRightLeftIterator iterator(&_partitions, which_partition);
result = allocate_with_affiliation(iterator, req.affiliation(), req, in_new_region);
}
if (result != nullptr) {
return result;
}
// No dice. Can we borrow space from mutator view?
if (!ShenandoahEvacReserveOverflow) {
return nullptr;
}
if (_partitions.get_empty_region_counts(ShenandoahFreeSetPartitionId::Mutator) > 0) {
// Try to steal an empty region from the mutator view.
result = try_allocate_from_mutator(req, in_new_region);
}
// This is it. Do not try to mix mutator and GC allocations, because adjusting region UWM
// due to GC allocations would expose unparsable mutator allocations.
return result;
}
HeapWord* ShenandoahFreeSet::try_allocate_from_mutator(ShenandoahAllocRequest& req, bool& in_new_region) {
// The collector prefers to keep longer lived regions toward the right side of the heap, so it always
// searches for regions from right to left here.
ShenandoahRightLeftIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator, true);
for (idx_t idx = iterator.current(); iterator.has_next(); idx = iterator.next()) {
ShenandoahHeapRegion* r = _heap->get_region(idx);
if (can_allocate_from(r)) {
if (req.is_old()) {
if (!flip_to_old_gc(r)) {
continue;
}
} else {
flip_to_gc(r);
}
// Region r is entirely empty. If try_allocate_in fails on region r, something else is really wrong.
// Don't bother to retry with other regions.
log_debug(gc, free)("Flipped region %zu to gc for request: " PTR_FORMAT, idx, p2i(&req));
return try_allocate_in(r, req, in_new_region);
}
}
return nullptr;
}
// This work method takes an argument corresponding to the number of bytes
// free in a region, and returns the largest amount in heapwords that can be allocated
// such that both of the following conditions are satisfied:
//
// 1. it is a multiple of card size
// 2. any remaining shard may be filled with a filler object
//
// The idea is that the allocation starts and ends at card boundaries. Because
// a region ('s end) is card-aligned, the remainder shard that must be filled is
// at the start of the free space.
//
// This is merely a helper method to use for the purpose of such a calculation.
size_t ShenandoahFreeSet::get_usable_free_words(size_t free_bytes) const {
// e.g. card_size is 512, card_shift is 9, min_fill_size() is 8
// free is 514
// usable_free is 512, which is decreased to 0
size_t usable_free = (free_bytes / CardTable::card_size()) << CardTable::card_shift();
assert(usable_free <= free_bytes, "Sanity check");
if ((free_bytes != usable_free) && (free_bytes - usable_free < ShenandoahHeap::min_fill_size() * HeapWordSize)) {
// After aligning to card multiples, the remainder would be smaller than
// the minimum filler object, so we'll need to take away another card's
// worth to construct a filler object.
if (usable_free >= CardTable::card_size()) {
usable_free -= CardTable::card_size();
} else {
assert(usable_free == 0, "usable_free is a multiple of card_size and card_size > min_fill_size");
}
}
return usable_free / HeapWordSize;
}
// Given a size argument, which is a multiple of card size, a request struct
// for a PLAB, and an old region, return a pointer to the allocated space for
// a PLAB which is card-aligned and where any remaining shard in the region
// has been suitably filled by a filler object.
// It is assumed (and assertion-checked) that such an allocation is always possible.
HeapWord* ShenandoahFreeSet::allocate_aligned_plab(size_t size, ShenandoahAllocRequest& req, ShenandoahHeapRegion* r) {
assert(_heap->mode()->is_generational(), "PLABs are only for generational mode");
assert(r->is_old(), "All PLABs reside in old-gen");
assert(!req.is_mutator_alloc(), "PLABs should not be allocated by mutators.");
assert(is_aligned(size, CardTable::card_size_in_words()), "Align by design");
HeapWord* result = r->allocate_aligned(size, req, CardTable::card_size());
assert(result != nullptr, "Allocation cannot fail");
assert(r->top() <= r->end(), "Allocation cannot span end of region");
assert(is_aligned(result, CardTable::card_size_in_words()), "Align by design");
return result;
}
HeapWord* ShenandoahFreeSet::try_allocate_in(ShenandoahHeapRegion* r, ShenandoahAllocRequest& req, bool& in_new_region) {
assert (has_alloc_capacity(r), "Performance: should avoid full regions on this path: %zu", r->index());
if (_heap->is_concurrent_weak_root_in_progress() && r->is_trash()) {
// We cannot use this region for allocation when weak roots are in progress because the collector may need
// to reference unmarked oops during concurrent classunloading. The collector also needs accurate marking
// information to determine which weak handles need to be null'd out. If the region is recycled before weak
// roots processing has finished, weak root processing may fail to null out a handle into a trashed region.
// This turns the handle into a dangling pointer and will crash or corrupt the heap.
return nullptr;
}
HeapWord* result = nullptr;
// We must call try_recycle_under_lock() even if !r->is_trash(). The reason is that if r is being recycled at this
// moment by a GC worker thread, it may appear to be not trash even though it has not yet been fully recycled. If
// we proceed without waiting for the worker to finish recycling the region, the worker thread may overwrite the
// region's affiliation with FREE after we set the region's affiliation to req.afiliation() below
r->try_recycle_under_lock();
in_new_region = r->is_empty();
if (in_new_region) {
log_debug(gc, free)("Using new region (%zu) for %s (" PTR_FORMAT ").",
r->index(), req.type_string(), p2i(&req));
assert(!r->is_affiliated(), "New region %zu should be unaffiliated", r->index());
r->set_affiliation(req.affiliation());
if (r->is_old()) {
// Any OLD region allocated during concurrent coalesce-and-fill does not need to be coalesced and filled because
// all objects allocated within this region are above TAMS (and thus are implicitly marked). In case this is an
// OLD region and concurrent preparation for mixed evacuations visits this region before the start of the next
// old-gen concurrent mark (i.e. this region is allocated following the start of old-gen concurrent mark but before
// concurrent preparations for mixed evacuations are completed), we mark this region as not requiring any
// coalesce-and-fill processing.
r->end_preemptible_coalesce_and_fill();
_heap->old_generation()->clear_cards_for(r);
}
#ifdef ASSERT
ShenandoahMarkingContext* const ctx = _heap->marking_context();
assert(ctx->top_at_mark_start(r) == r->bottom(), "Newly established allocation region starts with TAMS equal to bottom");
assert(ctx->is_bitmap_range_within_region_clear(ctx->top_bitmap(r), r->end()), "Bitmap above top_bitmap() must be clear");
#endif
log_debug(gc, free)("Using new region (%zu) for %s (" PTR_FORMAT ").",
r->index(), req.type_string(), p2i(&req));
} else {
assert(r->is_affiliated(), "Region %zu that is not new should be affiliated", r->index());
if (r->affiliation() != req.affiliation()) {
assert(_heap->mode()->is_generational(), "Request for %s from %s region should only happen in generational mode.",
req.affiliation_name(), r->affiliation_name());
return nullptr;
}
}
// req.size() is in words, r->free() is in bytes.
if (req.is_lab_alloc()) {
size_t adjusted_size = req.size();
size_t free = r->free(); // free represents bytes available within region r
if (req.is_old()) {
// This is a PLAB allocation(lab alloc in old gen)
assert(_heap->mode()->is_generational(), "PLABs are only for generational mode");
assert(_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, r->index()),
"PLABS must be allocated in old_collector_free regions");
// Need to assure that plabs are aligned on multiple of card region
// Convert free from unaligned bytes to aligned number of words
size_t usable_free = get_usable_free_words(free);
if (adjusted_size > usable_free) {
adjusted_size = usable_free;
}
adjusted_size = align_down(adjusted_size, CardTable::card_size_in_words());
if (adjusted_size >= req.min_size()) {
result = allocate_aligned_plab(adjusted_size, req, r);
assert(result != nullptr, "allocate must succeed");
req.set_actual_size(adjusted_size);
} else {
// Otherwise, leave result == nullptr because the adjusted size is smaller than min size.
log_trace(gc, free)("Failed to shrink PLAB request (%zu) in region %zu to %zu"
" because min_size() is %zu", req.size(), r->index(), adjusted_size, req.min_size());
}
} else {
// This is a GCLAB or a TLAB allocation
// Convert free from unaligned bytes to aligned number of words
free = align_down(free >> LogHeapWordSize, MinObjAlignment);
if (adjusted_size > free) {
adjusted_size = free;
}
if (adjusted_size >= req.min_size()) {
result = r->allocate(adjusted_size, req);
assert (result != nullptr, "Allocation must succeed: free %zu, actual %zu", free, adjusted_size);
req.set_actual_size(adjusted_size);
} else {
log_trace(gc, free)("Failed to shrink TLAB or GCLAB request (%zu) in region %zu to %zu"
" because min_size() is %zu", req.size(), r->index(), adjusted_size, req.min_size());
}
}
} else {
size_t size = req.size();
result = r->allocate(size, req);
if (result != nullptr) {
// Record actual allocation size
req.set_actual_size(size);
}
}
if (result != nullptr) {
// Allocation successful, bump stats:
if (req.is_mutator_alloc()) {
assert(req.is_young(), "Mutator allocations always come from young generation.");
_partitions.increase_used(ShenandoahFreeSetPartitionId::Mutator, req.actual_size() * HeapWordSize);
increase_bytes_allocated(req.actual_size() * HeapWordSize);
} else {
assert(req.is_gc_alloc(), "Should be gc_alloc since req wasn't mutator alloc");
// For GC allocations, we advance update_watermark because the objects relocated into this memory during
// evacuation are not updated during evacuation. For both young and old regions r, it is essential that all
// PLABs be made parsable at the end of evacuation. This is enabled by retiring all plabs at end of evacuation.
r->set_update_watermark(r->top());
if (r->is_old()) {
_partitions.increase_used(ShenandoahFreeSetPartitionId::OldCollector, (req.actual_size() + req.waste()) * HeapWordSize);
} else {
_partitions.increase_used(ShenandoahFreeSetPartitionId::Collector, (req.actual_size() + req.waste()) * HeapWordSize);
}
}
}
ShenandoahFreeSetPartitionId orig_partition;
if (req.is_mutator_alloc()) {
orig_partition = ShenandoahFreeSetPartitionId::Mutator;
} else if (req.is_old()) {
orig_partition = ShenandoahFreeSetPartitionId::OldCollector;
} else {
// Not old collector alloc, so this is a young collector gclab or shared allocation
orig_partition = ShenandoahFreeSetPartitionId::Collector;
}
if (alloc_capacity(r) < PLAB::min_size() * HeapWordSize) {
// Regardless of whether this allocation succeeded, if the remaining memory is less than PLAB:min_size(), retire this region.
// Note that retire_from_partition() increases used to account for waste.
size_t idx = r->index();
if ((result != nullptr) && in_new_region) {
_partitions.one_region_is_no_longer_empty(orig_partition);
}
size_t waste_bytes = _partitions.retire_from_partition(orig_partition, idx, r->used());
if (req.is_mutator_alloc() && (waste_bytes > 0)) {
increase_bytes_allocated(waste_bytes);
}
} else if ((result != nullptr) && in_new_region) {
_partitions.one_region_is_no_longer_empty(orig_partition);
}
switch (orig_partition) {
case ShenandoahFreeSetPartitionId::Mutator:
recompute_total_used</* UsedByMutatorChanged */ true,
/* UsedByCollectorChanged */ false, /* UsedByOldCollectorChanged */ false>();
if (in_new_region) {
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ false,
/* OldCollectorEmptiesChanged */ false, /* MutatorSizeChanged */ false,
/* CollectorSizeChanged */ false, /* OldCollectorSizeChanged */ false,
/* AffiliatedChangesAreYoungNeutral */ false, /* AffiliatedChangesAreGlobalNeutral */ false,
/* UnaffiliatedChangesAreYoungNeutral */ false>();
}
break;
case ShenandoahFreeSetPartitionId::Collector:
recompute_total_used</* UsedByMutatorChanged */ false,
/* UsedByCollectorChanged */ true, /* UsedByOldCollectorChanged */ false>();
if (in_new_region) {
recompute_total_affiliated</* MutatorEmptiesChanged */ false, /* CollectorEmptiesChanged */ true,
/* OldCollectorEmptiesChanged */ false, /* MutatorSizeChanged */ false,
/* CollectorSizeChanged */ false, /* OldCollectorSizeChanged */ false,
/* AffiliatedChangesAreYoungNeutral */ false, /* AffiliatedChangesAreGlobalNeutral */ false,
/* UnaffiliatedChangesAreYoungNeutral */ false>();
}
break;
case ShenandoahFreeSetPartitionId::OldCollector:
recompute_total_used</* UsedByMutatorChanged */ false,
/* UsedByCollectorChanged */ false, /* UsedByOldCollectorChanged */ true>();
if (in_new_region) {
recompute_total_affiliated</* MutatorEmptiesChanged */ false, /* CollectorEmptiesChanged */ false,
/* OldCollectorEmptiesChanged */ true, /* MutatorSizeChanged */ false,
/* CollectorSizeChanged */ false, /* OldCollectorSizeChanged */ false,
/* AffiliatedChangesAreYoungNeutral */ true, /* AffiliatedChangesAreGlobalNeutral */ false,
/* UnaffiliatedChangesAreYoungNeutral */ true>();
}
break;
case ShenandoahFreeSetPartitionId::NotFree:
default:
assert(false, "won't happen");
}
_partitions.assert_bounds();
return result;
}
HeapWord* ShenandoahFreeSet::allocate_contiguous(ShenandoahAllocRequest& req, bool is_humongous) {
assert(req.is_mutator_alloc(), "All contiguous allocations are performed by mutator");
shenandoah_assert_heaplocked();
size_t words_size = req.size();
idx_t num = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
assert(req.is_young(), "Humongous regions always allocated in YOUNG");
// Check if there are enough regions left to satisfy allocation.
if (num > (idx_t) _partitions.count(ShenandoahFreeSetPartitionId::Mutator)) {
return nullptr;
}
idx_t start_range = _partitions.leftmost_empty(ShenandoahFreeSetPartitionId::Mutator);
idx_t end_range = _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::Mutator) + 1;
idx_t last_possible_start = end_range - num;
// Find the continuous interval of $num regions, starting from $beg and ending in $end,
// inclusive. Contiguous allocations are biased to the beginning.
idx_t beg = _partitions.find_index_of_next_available_cluster_of_regions(ShenandoahFreeSetPartitionId::Mutator,
start_range, num);
if (beg > last_possible_start) {
// Hit the end, goodbye
return nullptr;
}
idx_t end = beg;
while (true) {
// We've confirmed num contiguous regions belonging to Mutator partition, so no need to confirm membership.
// If region is not completely free, the current [beg; end] is useless, and we may fast-forward. If we can extend
// the existing range, we can exploit that certain regions are already known to be in the Mutator free set.
while (!can_allocate_from(_heap->get_region(end))) {
// region[end] is not empty, so we restart our search after region[end]
idx_t slide_delta = end + 1 - beg;
if (beg + slide_delta > last_possible_start) {
// no room to slide
return nullptr;
}
for (idx_t span_end = beg + num; slide_delta > 0; slide_delta--) {
if (!_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, span_end)) {
beg = _partitions.find_index_of_next_available_cluster_of_regions(ShenandoahFreeSetPartitionId::Mutator,
span_end + 1, num);
break;
} else {
beg++;
span_end++;
}
}
// Here, either beg identifies a range of num regions all of which are in the Mutator free set, or beg > last_possible_start
if (beg > last_possible_start) {
// Hit the end, goodbye
return nullptr;
}
end = beg;
}
if ((end - beg + 1) == num) {
// found the match
break;
}
end++;
}
size_t total_used = 0;
const size_t used_words_in_last_region = words_size & ShenandoahHeapRegion::region_size_words_mask();
size_t waste_bytes;
// Retire regions from free partition and initialize them.
if (is_humongous) {
// Humongous allocation retires all regions at once: no allocation is possible anymore.
// retire_range_from_partition() will adjust bounds on Mutator free set if appropriate and will recompute affiliated.
_partitions.retire_range_from_partition(ShenandoahFreeSetPartitionId::Mutator, beg, end);
for (idx_t i = beg; i <= end; i++) {
ShenandoahHeapRegion* r = _heap->get_region(i);
assert(i == beg || _heap->get_region(i - 1)->index() + 1 == r->index(), "Should be contiguous");
r->try_recycle_under_lock();
assert(r->is_empty(), "Should be empty");
r->set_affiliation(req.affiliation());
if (i == beg) {
r->make_humongous_start();
} else {
r->make_humongous_cont();
}
if ((i == end) && (used_words_in_last_region > 0)) {
r->set_top(r->bottom() + used_words_in_last_region);
} else {
// if used_words_in_last_region is zero, then the end region is fully consumed.
r->set_top(r->end());
}
r->set_update_watermark(r->bottom());
}
total_used = ShenandoahHeapRegion::region_size_bytes() * num;
waste_bytes =
(used_words_in_last_region == 0)? 0: ShenandoahHeapRegion::region_size_bytes() - used_words_in_last_region * HeapWordSize;
} else {
// Non-humongous allocation retires only the regions that cannot be used for allocation anymore.
waste_bytes = 0;
for (idx_t i = beg; i <= end; i++) {
ShenandoahHeapRegion* r = _heap->get_region(i);
assert(i == beg || _heap->get_region(i - 1)->index() + 1 == r->index(), "Should be contiguous");
assert(r->is_empty(), "Should be empty");
r->try_recycle_under_lock();
r->set_affiliation(req.affiliation());
r->make_regular_allocation(req.affiliation());
if ((i == end) && (used_words_in_last_region > 0)) {
r->set_top(r->bottom() + used_words_in_last_region);
} else {
// if used_words_in_last_region is zero, then the end region is fully consumed.
r->set_top(r->end());
}
r->set_update_watermark(r->bottom());
total_used += r->used();
if (r->free() < PLAB::min_size() * HeapWordSize) {
// retire_from_partition() will adjust bounds on Mutator free set if appropriate and will recompute affiliated.
// It also increases used for the waste bytes, which includes bytes filled at retirement and bytes too small
// to be filled. Only the last iteration may have non-zero waste_bytes.
waste_bytes += _partitions.retire_from_partition(ShenandoahFreeSetPartitionId::Mutator, i, r->used());
}
}
_partitions.decrease_empty_region_counts(ShenandoahFreeSetPartitionId::Mutator, num);
if (waste_bytes > 0) {
// For humongous allocations, waste_bytes are included in total_used. Since this is not humongous,
// we need to account separately for the waste_bytes.
increase_bytes_allocated(waste_bytes);
}
}
_partitions.increase_used(ShenandoahFreeSetPartitionId::Mutator, total_used);
increase_bytes_allocated(total_used);
req.set_actual_size(words_size);
// If !is_humongous, the "waste" is made availabe for new allocation
if (waste_bytes > 0) {
req.set_waste(waste_bytes / HeapWordSize);
if (is_humongous) {
_partitions.increase_humongous_waste(ShenandoahFreeSetPartitionId::Mutator, waste_bytes);
_total_humongous_waste += waste_bytes;
}
}
recompute_total_young_used</* UsedByMutatorChanged */ true, /*UsedByCollectorChanged */ false>();
recompute_total_global_used</* UsedByMutatorChanged */ true, /*UsedByCollectorChanged */ false,
/* UsedByOldCollectorChanged */ true>();
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ false,
/* OldCollectorEmptiesChanged */ false, /* MutatorSizeChanged */ false,
/* CollectorSizeChanged */ false, /* OldCollectorSizeChanged */ false,
/* AffiliatedChangesAreYoungNeutral */ false, /* AffiliatedChangesAreGlobalNeutral */ false,
/* UnaffiliatedChangesAreYoungNeutral */ false>();
_partitions.assert_bounds();
return _heap->get_region(beg)->bottom();
}
class ShenandoahRecycleTrashedRegionClosure final : public ShenandoahHeapRegionClosure {
public:
void heap_region_do(ShenandoahHeapRegion* r) {
if (r->is_trash()) {
r->try_recycle();
}
}
bool is_thread_safe() {
return true;
}
};
void ShenandoahFreeSet::recycle_trash() {
// lock is not non-reentrant, check we don't have it
shenandoah_assert_not_heaplocked();
ShenandoahHeap* heap = ShenandoahHeap::heap();
heap->assert_gc_workers(heap->workers()->active_workers());
ShenandoahRecycleTrashedRegionClosure closure;
heap->parallel_heap_region_iterate(&closure);
}
bool ShenandoahFreeSet::transfer_one_region_from_mutator_to_old_collector(size_t idx, size_t alloc_capacity) {
ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
assert(alloc_capacity == region_size_bytes, "Region must be empty");
if (young_unaffiliated_regions() > 0) {
_partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
ShenandoahFreeSetPartitionId::OldCollector, alloc_capacity);
gen_heap->old_generation()->augment_evacuation_reserve(alloc_capacity);
recompute_total_used</* UsedByMutatorChanged */ true,
/* UsedByCollectorChanged */ false, /* UsedByOldCollectorChanged */ true>();
// Transferred region is unaffilliated, empty
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ false,
/* OldCollectorEmptiesChanged */ true, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ false, /* OldCollectorSizeChanged */ true,
/* AffiliatedChangesAreYoungNeutral */ true, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ false>();
_partitions.assert_bounds();
return true;
} else {
return false;
}
}
bool ShenandoahFreeSet::flip_to_old_gc(ShenandoahHeapRegion* r) {
const size_t idx = r->index();
assert(_partitions.partition_id_matches(idx, ShenandoahFreeSetPartitionId::Mutator), "Should be in mutator view");
assert(can_allocate_from(r), "Should not be allocated");
const size_t region_alloc_capacity = alloc_capacity(r);
if (transfer_one_region_from_mutator_to_old_collector(idx, region_alloc_capacity)) {
return true;
}
if (_heap->young_generation()->free_unaffiliated_regions() == 0 && _heap->old_generation()->free_unaffiliated_regions() > 0) {
// Old has free unaffiliated regions, but it couldn't use them for allocation (likely because they
// are trash and weak roots are in process). In this scenario, we aren't really stealing from the
// mutator (they have nothing to steal), but they do have a usable region in their partition. What
// we want to do here is swap that region from the mutator partition with one from the old collector
// partition.
// 1. Find a temporarily unusable trash region in the old collector partition
ShenandoahRightLeftIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::OldCollector, true);
idx_t unusable_trash = -1;
for (unusable_trash = iterator.current(); iterator.has_next(); unusable_trash = iterator.next()) {
const ShenandoahHeapRegion* region = _heap->get_region(unusable_trash);
if (region->is_trash() && _heap->is_concurrent_weak_root_in_progress()) {
break;
}
}
if (unusable_trash != -1) {
const size_t unusable_capacity = alloc_capacity(unusable_trash);
// 2. Move the (temporarily) unusable trash region we found to the mutator partition
_partitions.move_from_partition_to_partition(unusable_trash,
ShenandoahFreeSetPartitionId::OldCollector,
ShenandoahFreeSetPartitionId::Mutator, unusable_capacity);
// 3. Move this usable region from the mutator partition to the old collector partition
_partitions.move_from_partition_to_partition(idx,
ShenandoahFreeSetPartitionId::Mutator,
ShenandoahFreeSetPartitionId::OldCollector, region_alloc_capacity);
// Should have no effect on used, since flipped regions are trashed: zero used */
// Transferred regions are not affiliated, because they are empty (trash)
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ false,
/* OldCollectorEmptiesChanged */ true, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ false, /* OldCollectorSizeChanged */ true,
/* AffiliatedChangesAreYoungNeutral */ true, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ false>();
_partitions.assert_bounds();
// 4. Do not adjust capacities for generations, we just swapped the regions that have already
// been accounted for. However, we should adjust the evacuation reserves as those may have changed.
shenandoah_assert_heaplocked();
const size_t reserve = _heap->old_generation()->get_evacuation_reserve();
_heap->old_generation()->set_evacuation_reserve(reserve - unusable_capacity + region_alloc_capacity);
return true;
}
}
// We can't take this region young because it has no free unaffiliated regions (transfer failed).
return false;
}
void ShenandoahFreeSet::flip_to_gc(ShenandoahHeapRegion* r) {
size_t idx = r->index();
assert(_partitions.partition_id_matches(idx, ShenandoahFreeSetPartitionId::Mutator), "Should be in mutator view");
assert(can_allocate_from(r), "Should not be allocated");
size_t ac = alloc_capacity(r);
_partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
ShenandoahFreeSetPartitionId::Collector, ac);
recompute_total_used</* UsedByMutatorChanged */ true,
/* UsedByCollectorChanged */ false, /* UsedByOldCollectorChanged */ true>();
// Transfer only affects unaffiliated regions, which stay in young
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ true,
/* OldCollectorEmptiesChanged */ false, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ true, /* OldCollectorSizeChanged */ false,
/* AffiliatedChangesAreYoungNeutral */ true, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ true>();
_partitions.assert_bounds();
// We do not ensure that the region is no longer trash, relying on try_allocate_in(), which always comes next,
// to recycle trash before attempting to allocate anything in the region.
}
void ShenandoahFreeSet::clear() {
clear_internal();
}
void ShenandoahFreeSet::clear_internal() {
shenandoah_assert_heaplocked();
_partitions.make_all_regions_unavailable();
recompute_total_used</* UsedByMutatorChanged */ true,
/* UsedByCollectorChanged */ true, /* UsedByOldCollectorChanged */ true>();
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ true,
/* OldCollectorEmptiesChanged */ true, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ true, /* OldCollectorSizeChanged */ true,
/* AffiliatedChangesAreYoungNeutral */ true, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ true>();
_alloc_bias_weight = 0;
_partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::Mutator, true);
_partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::Collector, false);
_partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::OldCollector, false);
}
// Returns total allocatable words in Mutator partition
size_t ShenandoahFreeSet::find_regions_with_alloc_capacity(size_t &young_trashed_regions, size_t &old_trashed_regions,
size_t &first_old_region, size_t &last_old_region,
size_t &old_region_count) {
// This resets all state information, removing all regions from all sets.
clear_internal();
first_old_region = _heap->num_regions();
last_old_region = 0;
old_region_count = 0;
old_trashed_regions = 0;
young_trashed_regions = 0;
size_t old_cset_regions = 0;
size_t young_cset_regions = 0;
size_t region_size_bytes = _partitions.region_size_bytes();
size_t max_regions = _partitions.max();
size_t mutator_alloc_capacity_in_words = 0;
size_t mutator_leftmost = max_regions;
size_t mutator_rightmost = 0;
size_t mutator_leftmost_empty = max_regions;
size_t mutator_rightmost_empty = 0;
size_t old_collector_leftmost = max_regions;
size_t old_collector_rightmost = 0;
size_t old_collector_leftmost_empty = max_regions;
size_t old_collector_rightmost_empty = 0;
size_t mutator_empty = 0;
size_t old_collector_empty = 0;
// These two variables represent the total used within each partition, including humongous waste and retired regions
size_t mutator_used = 0;
size_t old_collector_used = 0;
// These two variables represent memory that is wasted within humongous regions due to alignment padding
size_t mutator_humongous_waste = 0;
size_t old_collector_humongous_waste = 0;
// These two variables track regions that have allocatable memory
size_t mutator_regions = 0;
size_t old_collector_regions = 0;
// These two variables track regions that are not empty within each partition
size_t affiliated_mutator_regions = 0;
size_t affiliated_old_collector_regions = 0;
// These two variables represent the total capacity of each partition, including retired regions
size_t total_mutator_regions = 0;
size_t total_old_collector_regions = 0;
size_t num_regions = _heap->num_regions();
for (size_t idx = 0; idx < num_regions; idx++) {
ShenandoahHeapRegion* region = _heap->get_region(idx);
if (region->is_trash()) {
// Trashed regions represent regions that had been in the collection set (or may have been identified as immediate garbage)
// but have not yet been "cleaned up". The cset regions are not "trashed" until we have finished update refs.
if (region->is_old()) {
// We're going to place this region into the Mutator set. We increment old_trashed_regions because this count represents
// regions that the old generation is entitled to without any transfer from young. We do not place this region into
// the OldCollector partition at this time. Instead, we let reserve_regions() decide whether to place this region
// into the OldCollector partition. Deferring the decision allows reserve_regions() to more effectively pack the
// OldCollector regions into high-address memory. We do not adjust capacities of old and young generations at this
// time. At the end of finish_rebuild(), the capacities are adjusted based on the results of reserve_regions().
old_trashed_regions++;
} else {
assert(region->is_young(), "Trashed region should be old or young");
young_trashed_regions++;
}
} else if (region->is_old()) {
// We count humongous and regular regions as "old regions". We do not count trashed regions that are old. Those
// are counted (above) as old_trashed_regions.
old_region_count++;
if (first_old_region > idx) {
first_old_region = idx;
}
last_old_region = idx;
}
if (region->is_alloc_allowed() || region->is_trash()) {
assert(!region->is_cset(), "Shouldn't be adding cset regions to the free set");
// Do not add regions that would almost surely fail allocation
size_t ac = alloc_capacity(region);
if (ac >= PLAB::min_size() * HeapWordSize) {
if (region->is_trash() || !region->is_old()) {
// Both young and old (possibly immediately) collected regions (trashed) are placed into the Mutator set
_partitions.raw_assign_membership(idx, ShenandoahFreeSetPartitionId::Mutator);
mutator_alloc_capacity_in_words += ac / HeapWordSize;
if (idx < mutator_leftmost) {
mutator_leftmost = idx;
}
if (idx > mutator_rightmost) {
mutator_rightmost = idx;
}
if (ac == region_size_bytes) {
mutator_empty++;
if (idx < mutator_leftmost_empty) {
mutator_leftmost_empty = idx;
}
if (idx > mutator_rightmost_empty) {
mutator_rightmost_empty = idx;
}
} else {
affiliated_mutator_regions++;
}
mutator_regions++;
total_mutator_regions++;
mutator_used += (region_size_bytes - ac);
} else {
// !region->is_trash() && region is_old()
_partitions.raw_assign_membership(idx, ShenandoahFreeSetPartitionId::OldCollector);
if (idx < old_collector_leftmost) {
old_collector_leftmost = idx;
}
if (idx > old_collector_rightmost) {
old_collector_rightmost = idx;
}
assert(ac != region_size_bytes, "Empty regions should be in mutator partition");
affiliated_old_collector_regions++;
old_collector_regions++;
total_old_collector_regions++;
old_collector_used += region_size_bytes - ac;
}
} else {
// This region does not have enough free to be part of the free set. Count all of its memory as used.
assert(_partitions.membership(idx) == ShenandoahFreeSetPartitionId::NotFree, "Region should have been retired");
if (region->is_old()) {
old_collector_used += region_size_bytes;
total_old_collector_regions++;
affiliated_old_collector_regions++;
} else {
mutator_used += region_size_bytes;
total_mutator_regions++;
affiliated_mutator_regions++;
}
}
} else {
// This region does not allow allocation (it is retired or is humongous or is in cset).
// Retired and humongous regions generally have no alloc capacity, but cset regions may have large alloc capacity.
if (region->is_cset()) {
if (region->is_old()) {
old_cset_regions++;
} else {
young_cset_regions++;
}
} else {
assert(_partitions.membership(idx) == ShenandoahFreeSetPartitionId::NotFree, "Region should have been retired");
size_t humongous_waste_bytes = 0;
if (region->is_humongous_start()) {
// Since rebuild does not necessarily happen at a safepoint, a newly allocated humongous object may not have been
// fully initialized. Therefore, we cannot safely consult its header.
ShenandoahHeapRegion* last_of_humongous_continuation = region;
size_t next_idx;
for (next_idx = idx + 1; next_idx < num_regions; next_idx++) {
ShenandoahHeapRegion* humongous_cont_candidate = _heap->get_region(next_idx);
if (!humongous_cont_candidate->is_humongous_continuation()) {
break;
}
last_of_humongous_continuation = humongous_cont_candidate;
}
// For humongous regions, used() is established while holding the global heap lock so it is reliable here
humongous_waste_bytes = ShenandoahHeapRegion::region_size_bytes() - last_of_humongous_continuation->used();
}
if (region->is_old()) {
old_collector_used += region_size_bytes;
total_old_collector_regions++;
old_collector_humongous_waste += humongous_waste_bytes;
affiliated_old_collector_regions++;
} else {
mutator_used += region_size_bytes;
total_mutator_regions++;
mutator_humongous_waste += humongous_waste_bytes;
affiliated_mutator_regions++;
}
}
}
}
// At the start of evacuation, the cset regions are not counted as part of Mutator or OldCollector partitions.
// At the end of GC, when we rebuild rebuild freeset (which happens before we have recycled the collection set), we treat
// all cset regions as part of capacity, as fully available, as unaffiliated. We place trashed regions into the Mutator
// partition.
// No need to update generation sizes here. These are the sizes already recognized by the generations. These
// adjustments allow the freeset tallies to match the generation tallies.
log_debug(gc, free)(" At end of prep_to_rebuild, mutator_leftmost: %zu"
", mutator_rightmost: %zu"
", mutator_leftmost_empty: %zu"
", mutator_rightmost_empty: %zu"
", mutator_regions: %zu"
", mutator_used: %zu",
mutator_leftmost, mutator_rightmost, mutator_leftmost_empty, mutator_rightmost_empty,
mutator_regions, mutator_used);
log_debug(gc, free)(" old_collector_leftmost: %zu"
", old_collector_rightmost: %zu"
", old_collector_leftmost_empty: %zu"
", old_collector_rightmost_empty: %zu"
", old_collector_regions: %zu"
", old_collector_used: %zu",
old_collector_leftmost, old_collector_rightmost, old_collector_leftmost_empty, old_collector_rightmost_empty,
old_collector_regions, old_collector_used);
log_debug(gc, free)(" total_mutator_regions: %zu, total_old_collector_regions: %zu"
", mutator_empty: %zu, old_collector_empty: %zu",
total_mutator_regions, total_old_collector_regions, mutator_empty, old_collector_empty);
idx_t rightmost_idx = (mutator_leftmost == max_regions)? -1: (idx_t) mutator_rightmost;
idx_t rightmost_empty_idx = (mutator_leftmost_empty == max_regions)? -1: (idx_t) mutator_rightmost_empty;
_partitions.establish_mutator_intervals(mutator_leftmost, rightmost_idx, mutator_leftmost_empty, rightmost_empty_idx,
total_mutator_regions + young_cset_regions, mutator_empty, mutator_regions,
mutator_used + young_cset_regions * region_size_bytes, mutator_humongous_waste);
rightmost_idx = (old_collector_leftmost == max_regions)? -1: (idx_t) old_collector_rightmost;
rightmost_empty_idx = (old_collector_leftmost_empty == max_regions)? -1: (idx_t) old_collector_rightmost_empty;
_partitions.establish_old_collector_intervals(old_collector_leftmost, rightmost_idx,
old_collector_leftmost_empty, rightmost_empty_idx,
total_old_collector_regions + old_cset_regions,
old_collector_empty, old_collector_regions,
old_collector_used + old_cset_regions * region_size_bytes,
old_collector_humongous_waste);
_total_humongous_waste = mutator_humongous_waste + old_collector_humongous_waste;
_total_young_regions = total_mutator_regions + young_cset_regions;
_total_global_regions = _total_young_regions + total_old_collector_regions + old_cset_regions;
recompute_total_used</* UsedByMutatorChanged */ true,
/* UsedByCollectorChanged */ true, /* UsedByOldCollectorChanged */ true>();
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ true,
/* OldCollectorEmptiesChanged */ true, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ true, /* OldCollectorSizeChanged */ true,
/* AffiliatedChangesAreYoungNeutral */ false, /* AffiliatedChangesAreGlobalNeutral */ false,
/* UnaffiliatedChangesAreYoungNeutral */ false>();
_partitions.assert_bounds();
#ifdef ASSERT
if (_heap->mode()->is_generational()) {
assert(young_affiliated_regions() == _heap->young_generation()->get_affiliated_region_count(), "sanity");
} else {
assert(young_affiliated_regions() == _heap->global_generation()->get_affiliated_region_count(), "sanity");
}
#endif
log_debug(gc, free)(" After find_regions_with_alloc_capacity(), Mutator range [%zd, %zd],"
" Old Collector range [%zd, %zd]",
_partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
_partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector));
return mutator_alloc_capacity_in_words;
}
void ShenandoahFreeSet::transfer_humongous_regions_from_mutator_to_old_collector(size_t xfer_regions,
size_t humongous_waste_bytes) {
shenandoah_assert_heaplocked();
size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
_partitions.decrease_humongous_waste(ShenandoahFreeSetPartitionId::Mutator, humongous_waste_bytes);
_partitions.decrease_used(ShenandoahFreeSetPartitionId::Mutator, xfer_regions * region_size_bytes);
_partitions.decrease_capacity(ShenandoahFreeSetPartitionId::Mutator, xfer_regions * region_size_bytes);
_partitions.increase_capacity(ShenandoahFreeSetPartitionId::OldCollector, xfer_regions * region_size_bytes);
_partitions.increase_humongous_waste(ShenandoahFreeSetPartitionId::OldCollector, humongous_waste_bytes);
_partitions.increase_used(ShenandoahFreeSetPartitionId::OldCollector, xfer_regions * region_size_bytes);
// _total_humongous_waste, _total_global_regions are unaffected by transfer
_total_young_regions -= xfer_regions;
recompute_total_young_used</* UsedByMutatorChanged */ true, /* UsedByCollectorChanged */ false>();
recompute_total_old_used</* UsedByOldCollectorChanged */ true>();
recompute_total_affiliated</* MutatorEmptiesChanged */ false, /* CollectorEmptiesChanged */ false,
/* OldCollectorEmptiesChanged */ false, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ false, /* OldCollectorSizeChanged */ true,
/* AffiliatedChangesAreYoungNeutral */ false, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ true>();
_partitions.assert_bounds();
// global_used is unaffected by this transfer
// No need to adjust ranges because humongous regions are not allocatable
}
void ShenandoahFreeSet::transfer_empty_regions_from_to(ShenandoahFreeSetPartitionId source,
ShenandoahFreeSetPartitionId dest,
size_t num_regions) {
assert(dest != source, "precondition");
shenandoah_assert_heaplocked();
const size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
size_t transferred_regions = 0;
size_t used_transfer = 0;
idx_t source_low_idx = _partitions.max();
idx_t source_high_idx = -1;
idx_t dest_low_idx = _partitions.max();
idx_t dest_high_idx = -1;
ShenandoahLeftRightIterator iterator(&_partitions, source, true);
for (idx_t idx = iterator.current(); transferred_regions < num_regions && iterator.has_next(); idx = iterator.next()) {
// Note: can_allocate_from() denotes that region is entirely empty
if (can_allocate_from(idx)) {
if (idx < source_low_idx) {
source_low_idx = idx;
}
if (idx > source_high_idx) {
source_high_idx = idx;
}
if (idx < dest_low_idx) {
dest_low_idx = idx;
}
if (idx > dest_high_idx) {
dest_high_idx = idx;
}
used_transfer += _partitions.move_from_partition_to_partition_with_deferred_accounting(idx, source, dest, region_size_bytes);
transferred_regions++;
}
}
// All transferred regions are empty.
assert(used_transfer == 0, "empty regions should have no used");
_partitions.expand_interval_if_range_modifies_either_boundary(dest, dest_low_idx,
dest_high_idx, dest_low_idx, dest_high_idx);
_partitions.shrink_interval_if_range_modifies_either_boundary(source, source_low_idx, source_high_idx,
transferred_regions);
_partitions.decrease_region_counts(source, transferred_regions);
_partitions.decrease_empty_region_counts(source, transferred_regions);
_partitions.decrease_capacity(source, transferred_regions * region_size_bytes);
_partitions.increase_capacity(dest, transferred_regions * region_size_bytes);
_partitions.increase_region_counts(dest, transferred_regions);
_partitions.increase_empty_region_counts(dest, transferred_regions);
// Since only empty regions are transferred, no need to recompute_total_used()
if (source == ShenandoahFreeSetPartitionId::OldCollector) {
assert((dest == ShenandoahFreeSetPartitionId::Collector) || (dest == ShenandoahFreeSetPartitionId::Mutator), "sanity");
_total_young_regions += transferred_regions;
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ true,
/* OldCollectorEmptiesChanged */ true, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ true, /* OldCollectorSizeChanged */ true,
/* AffiliatedChangesAreYoungNeutral */ true, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ false>();
} else {
assert((source == ShenandoahFreeSetPartitionId::Collector) || (source == ShenandoahFreeSetPartitionId::Mutator), "sanity");
if (dest == ShenandoahFreeSetPartitionId::OldCollector) {
_total_young_regions -= transferred_regions;
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ true,
/* OldCollectorEmptiesChanged */ true, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ true, /* OldCollectorSizeChanged */ true,
/* AffiliatedChangesAreYoungNeutral */ true, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ false>();
} else {
assert((dest == ShenandoahFreeSetPartitionId::Collector) || (dest == ShenandoahFreeSetPartitionId::Mutator), "sanity");
// No adjustments to total_young_regions if transferring within young
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ true,
/* OldCollectorEmptiesChanged */ false, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ true, /* OldCollectorSizeChanged */ false,
/* AffiliatedChangesAreYoungNeutral */ true, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ true>();
}
}
_partitions.assert_bounds();
}
// Returns number of regions transferred, adds transferred bytes to var argument bytes_transferred
size_t ShenandoahFreeSet::transfer_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId which_collector,
size_t max_xfer_regions,
size_t& bytes_transferred) {
shenandoah_assert_heaplocked();
const size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
size_t transferred_regions = 0;
size_t used_transfer = 0;
idx_t collector_low_idx = _partitions.max();
idx_t collector_high_idx = -1;
idx_t mutator_low_idx = _partitions.max();
idx_t mutator_high_idx = -1;
ShenandoahLeftRightIterator iterator(&_partitions, which_collector, true);
for (idx_t idx = iterator.current(); transferred_regions < max_xfer_regions && iterator.has_next(); idx = iterator.next()) {
// Note: can_allocate_from() denotes that region is entirely empty
if (can_allocate_from(idx)) {
if (idx < collector_low_idx) {
collector_low_idx = idx;
}
if (idx > collector_high_idx) {
collector_high_idx = idx;
}
if (idx < mutator_low_idx) {
mutator_low_idx = idx;
}
if (idx > mutator_high_idx) {
mutator_high_idx = idx;
}
used_transfer += _partitions.move_from_partition_to_partition_with_deferred_accounting(idx, which_collector,
ShenandoahFreeSetPartitionId::Mutator,
region_size_bytes);
transferred_regions++;
bytes_transferred += region_size_bytes;
}
}
// All transferred regions are empty.
assert(used_transfer == 0, "empty regions should have no used");
_partitions.expand_interval_if_range_modifies_either_boundary(ShenandoahFreeSetPartitionId::Mutator, mutator_low_idx,
mutator_high_idx, mutator_low_idx, mutator_high_idx);
_partitions.shrink_interval_if_range_modifies_either_boundary(which_collector, collector_low_idx, collector_high_idx,
transferred_regions);
_partitions.decrease_region_counts(which_collector, transferred_regions);
_partitions.decrease_empty_region_counts(which_collector, transferred_regions);
_partitions.decrease_capacity(which_collector, transferred_regions * region_size_bytes);
_partitions.increase_capacity(ShenandoahFreeSetPartitionId::Mutator, transferred_regions * region_size_bytes);
_partitions.increase_region_counts(ShenandoahFreeSetPartitionId::Mutator, transferred_regions);
_partitions.increase_empty_region_counts(ShenandoahFreeSetPartitionId::Mutator, transferred_regions);
if (which_collector == ShenandoahFreeSetPartitionId::OldCollector) {
_total_young_regions += transferred_regions;
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ false,
/* OldCollectorEmptiesChanged */ true, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ false, /* OldCollectorSizeChanged */ true,
/* AffiliatedChangesAreYoungNeutral */ true, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ false>();
} else {
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ true,
/* OldCollectorEmptiesChanged */ false, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ true, /* OldCollectorSizeChanged */ false,
/* AffiliatedChangesAreYoungNeutral */ true, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ true>();
}
_partitions.assert_bounds();
return transferred_regions;
}
// Returns number of regions transferred, adds transferred bytes to var argument bytes_transferred
size_t ShenandoahFreeSet::
transfer_non_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId which_collector,
size_t max_xfer_regions, size_t& bytes_transferred) {
shenandoah_assert_heaplocked();
size_t region_size_bytes = _partitions.region_size_bytes();
size_t transferred_regions = 0;
size_t used_transfer = 0;
idx_t collector_low_idx = _partitions.max();
idx_t collector_high_idx = -1;
idx_t mutator_low_idx = _partitions.max();
idx_t mutator_high_idx = -1;
ShenandoahLeftRightIterator iterator(&_partitions, which_collector, false);
for (idx_t idx = iterator.current(); transferred_regions < max_xfer_regions && iterator.has_next(); idx = iterator.next()) {
size_t ac = alloc_capacity(idx);
if (ac > 0) {
if (idx < collector_low_idx) {
collector_low_idx = idx;
}
if (idx > collector_high_idx) {
collector_high_idx = idx;
}
if (idx < mutator_low_idx) {
mutator_low_idx = idx;
}
if (idx > mutator_high_idx) {
mutator_high_idx = idx;
}
assert (ac < region_size_bytes, "Move empty regions with different function");
used_transfer += _partitions.move_from_partition_to_partition_with_deferred_accounting(idx, which_collector,
ShenandoahFreeSetPartitionId::Mutator,
ac);
transferred_regions++;
bytes_transferred += ac;
}
}
// _empty_region_counts is unaffected, because we transfer only non-empty regions here.
_partitions.decrease_used(which_collector, used_transfer);
_partitions.expand_interval_if_range_modifies_either_boundary(ShenandoahFreeSetPartitionId::Mutator,
mutator_low_idx, mutator_high_idx, _partitions.max(), -1);
_partitions.shrink_interval_if_range_modifies_either_boundary(which_collector, collector_low_idx, collector_high_idx,
transferred_regions);
_partitions.decrease_region_counts(which_collector, transferred_regions);
_partitions.decrease_capacity(which_collector, transferred_regions * region_size_bytes);
_partitions.increase_capacity(ShenandoahFreeSetPartitionId::Mutator, transferred_regions * region_size_bytes);
_partitions.increase_region_counts(ShenandoahFreeSetPartitionId::Mutator, transferred_regions);
_partitions.increase_used(ShenandoahFreeSetPartitionId::Mutator, used_transfer);
if (which_collector == ShenandoahFreeSetPartitionId::OldCollector) {
_total_young_regions += transferred_regions;
}
// _total_global_regions unaffected by transfer
recompute_total_used</* UsedByMutatorChanged */ true,
/* UsedByCollectorChanged */ true, /* UsedByOldCollectorChanged */ true>();
// All transfers are affiliated
if (which_collector == ShenandoahFreeSetPartitionId::OldCollector) {
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollectorEmptiesChanged */ false,
/* OldCollectorEmptiesChanged */ true, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ false, /* OldCollectorSizeChanged */ true,
/* AffiliatedChangesAreYoungNeutral */ false, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ true>();
} else {
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollecteorEmptiesChanged */true,
/* OldCollectorEmptiesChanged */ false, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ true, /* OldCollectorSizeChanged */ false,
/* AffiliatedChangesAreYoungNeutral */ true, /* AffiliatedChangesAreGlobalNeutral */ true,
/* UnaffiliatedChangesAreYoungNeutral */ true>();
}
_partitions.assert_bounds();
return transferred_regions;
}
void ShenandoahFreeSet::move_regions_from_collector_to_mutator(size_t max_xfer_regions) {
size_t collector_xfer = 0;
size_t old_collector_xfer = 0;
// Process empty regions within the Collector free partition
if ((max_xfer_regions > 0) &&
(_partitions.leftmost_empty(ShenandoahFreeSetPartitionId::Collector)
<= _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::Collector))) {
ShenandoahHeapLocker locker(_heap->lock());
max_xfer_regions -=
transfer_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId::Collector, max_xfer_regions,
collector_xfer);
}
// Process empty regions within the OldCollector free partition
if ((max_xfer_regions > 0) &&
(_partitions.leftmost_empty(ShenandoahFreeSetPartitionId::OldCollector)
<= _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::OldCollector))) {
ShenandoahHeapLocker locker(_heap->lock());
size_t old_collector_regions =
transfer_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId::OldCollector, max_xfer_regions,
old_collector_xfer);
max_xfer_regions -= old_collector_regions;
}
// If there are any non-empty regions within Collector partition, we can also move them to the Mutator free partition
if ((max_xfer_regions > 0) && (_partitions.leftmost(ShenandoahFreeSetPartitionId::Collector)
<= _partitions.rightmost(ShenandoahFreeSetPartitionId::Collector))) {
ShenandoahHeapLocker locker(_heap->lock());
max_xfer_regions -=
transfer_non_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId::Collector, max_xfer_regions,
collector_xfer);
}
size_t total_xfer = collector_xfer + old_collector_xfer;
log_info(gc, ergo)("At start of update refs, moving %zu%s to Mutator free set from Collector Reserve ("
"%zu%s) and from Old Collector Reserve (%zu%s)",
byte_size_in_proper_unit(total_xfer), proper_unit_for_byte_size(total_xfer),
byte_size_in_proper_unit(collector_xfer), proper_unit_for_byte_size(collector_xfer),
byte_size_in_proper_unit(old_collector_xfer), proper_unit_for_byte_size(old_collector_xfer));
}
// Overwrite arguments to represent the amount of memory in each generation that is about to be recycled
void ShenandoahFreeSet::prepare_to_rebuild(size_t &young_trashed_regions, size_t &old_trashed_regions,
size_t &first_old_region, size_t &last_old_region, size_t &old_region_count) {
shenandoah_assert_heaplocked();
assert(rebuild_lock() != nullptr, "sanity");
rebuild_lock()->lock(false);
// This resets all state information, removing all regions from all sets.
clear();
log_debug(gc, free)("Rebuilding FreeSet");
// Place regions that have alloc_capacity into the old_collector set if they identify as is_old() or the
// mutator set otherwise. All trashed (cset) regions are affiliated young and placed in mutator set. Save the
// allocatable words in mutator partition in state variable.
_prepare_to_rebuild_mutator_free = find_regions_with_alloc_capacity(young_trashed_regions, old_trashed_regions,
first_old_region, last_old_region, old_region_count);
}
// Return mutator free
void ShenandoahFreeSet::finish_rebuild(size_t young_trashed_regions, size_t old_trashed_regions, size_t old_region_count) {
shenandoah_assert_heaplocked();
size_t young_reserve(0), old_reserve(0);
if (_heap->mode()->is_generational()) {
compute_young_and_old_reserves(young_trashed_regions, old_trashed_regions, young_reserve, old_reserve);
} else {
young_reserve = (_heap->max_capacity() / 100) * ShenandoahEvacReserve;
old_reserve = 0;
}
// Move some of the mutator regions into the Collector and OldCollector partitions in order to satisfy
// young_reserve and old_reserve.
size_t young_used_regions, old_used_regions, young_used_bytes, old_used_bytes;
reserve_regions(young_reserve, old_reserve, old_region_count, young_used_regions, old_used_regions,
young_used_bytes, old_used_bytes);
_total_young_regions = _heap->num_regions() - old_region_count;
_total_global_regions = _heap->num_regions();
establish_old_collector_alloc_bias();
// Release the rebuild lock now. What remains in this function is read-only
rebuild_lock()->unlock();
_partitions.assert_bounds();
log_status();
if (_heap->mode()->is_generational()) {
// Clear the region balance until it is adjusted in preparation for a subsequent GC cycle.
_heap->old_generation()->set_region_balance(0);
}
}
// Reduce old reserve (when there are insufficient resources to satisfy the original request).
void ShenandoahFreeSet::reduce_old_reserve(size_t adjusted_old_reserve, size_t requested_old_reserve) {
ShenandoahOldGeneration* const old_generation = _heap->old_generation();
size_t requested_promoted_reserve = old_generation->get_promoted_reserve();
size_t requested_old_evac_reserve = old_generation->get_evacuation_reserve();
assert(adjusted_old_reserve < requested_old_reserve, "Only allow reduction");
assert(requested_promoted_reserve + requested_old_evac_reserve >= adjusted_old_reserve, "Sanity");
size_t delta = requested_old_reserve - adjusted_old_reserve;
if (requested_promoted_reserve >= delta) {
requested_promoted_reserve -= delta;
old_generation->set_promoted_reserve(requested_promoted_reserve);
} else {
delta -= requested_promoted_reserve;
requested_promoted_reserve = 0;
requested_old_evac_reserve -= delta;
old_generation->set_promoted_reserve(requested_promoted_reserve);
old_generation->set_evacuation_reserve(requested_old_evac_reserve);
}
}
// Reduce young reserve (when there are insufficient resources to satisfy the original request).
void ShenandoahFreeSet::reduce_young_reserve(size_t adjusted_young_reserve, size_t requested_young_reserve) {
ShenandoahYoungGeneration* const young_generation = _heap->young_generation();
assert(adjusted_young_reserve < requested_young_reserve, "Only allow reduction");
young_generation->set_evacuation_reserve(adjusted_young_reserve);
}
/**
* Set young_reserve_result and old_reserve_result to the number of bytes that we desire to set aside to hold the
* results of evacuation to young and old collector spaces respectively during the next evacuation phase. Overwrite
* old_generation region balance in case the original value is incompatible with the current reality.
*
* These values are determined by how much memory is currently available within each generation, which is
* represented by:
* 1. Memory currently available within old and young
* 2. Trashed regions currently residing in young and old, which will become available momentarily
* 3. The value of old_generation->get_region_balance() which represents the number of regions that we plan
* to transfer from old generation to young generation. Prior to each invocation of compute_young_and_old_reserves(),
* this value should computed by ShenandoahGenerationalHeap::compute_old_generation_balance().
*/
void ShenandoahFreeSet::compute_young_and_old_reserves(size_t young_trashed_regions, size_t old_trashed_regions,
size_t& young_reserve_result, size_t& old_reserve_result) const {
shenandoah_assert_generational();
shenandoah_assert_heaplocked();
const size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
ShenandoahOldGeneration* const old_generation = _heap->old_generation();
size_t old_available = old_generation->available();
size_t old_unaffiliated_regions = old_generation->free_unaffiliated_regions();
ShenandoahYoungGeneration* const young_generation = _heap->young_generation();
size_t young_capacity = young_generation->max_capacity();
size_t young_unaffiliated_regions = young_generation->free_unaffiliated_regions();
// Add in the regions we anticipate to be freed by evacuation of the collection set
old_unaffiliated_regions += old_trashed_regions;
old_available += old_trashed_regions * region_size_bytes;
young_unaffiliated_regions += young_trashed_regions;
assert(young_capacity >= young_generation->used(),
"Young capacity (%zu) must exceed used (%zu)", young_capacity, young_generation->used());
size_t young_available = young_capacity - young_generation->used();
young_available += young_trashed_regions * region_size_bytes;
assert(young_available >= young_unaffiliated_regions * region_size_bytes, "sanity");
assert(old_available >= old_unaffiliated_regions * region_size_bytes, "sanity");
// Consult old-region balance to make adjustments to current generation capacities and availability.
// The generation region transfers take place after we rebuild. old_region_balance represents number of regions
// to transfer from old to young.
ssize_t old_region_balance = old_generation->get_region_balance();
if (old_region_balance != 0) {
#ifdef ASSERT
if (old_region_balance > 0) {
assert(old_region_balance <= checked_cast<ssize_t>(old_unaffiliated_regions),
"Cannot transfer %zd regions that are affiliated (old_trashed: %zu, old_unaffiliated: %zu)",
old_region_balance, old_trashed_regions, old_unaffiliated_regions);
} else {
assert(0 - old_region_balance <= checked_cast<ssize_t>(young_unaffiliated_regions),
"Cannot transfer regions that are affiliated");
}
#endif
ssize_t xfer_bytes = old_region_balance * checked_cast<ssize_t>(region_size_bytes);
old_available -= xfer_bytes;
old_unaffiliated_regions -= old_region_balance;
young_available += xfer_bytes;
young_capacity += xfer_bytes;
young_unaffiliated_regions += old_region_balance;
}
// All allocations taken from the old collector set are performed by GC, generally using PLABs for both
// promotions and evacuations. The partition between which old memory is reserved for evacuation and
// which is reserved for promotion is enforced using thread-local variables that prescribe intentions for
// each PLAB's available memory.
const size_t promoted_reserve = old_generation->get_promoted_reserve();
const size_t old_evac_reserve = old_generation->get_evacuation_reserve();
young_reserve_result = young_generation->get_evacuation_reserve();
old_reserve_result = promoted_reserve + old_evac_reserve;
assert(old_reserve_result + young_reserve_result <= old_available + young_available,
"Cannot reserve (%zu + %zu + %zu) more than is available: %zu + %zu",
promoted_reserve, old_evac_reserve, young_reserve_result, old_available, young_available);
// Old available regions that have less than PLAB::min_size() of available memory are not placed into the OldCollector
// free set. Because of this, old_available may not have enough memory to represent the intended reserve. Adjust
// the reserve downward to account for this possibility. This loss is part of the reason why the original budget
// was adjusted with ShenandoahOldEvacWaste and ShenandoahOldPromoWaste multipliers.
if (old_reserve_result >
_partitions.available_in(ShenandoahFreeSetPartitionId::OldCollector) + old_unaffiliated_regions * region_size_bytes) {
old_reserve_result =
_partitions.available_in(ShenandoahFreeSetPartitionId::OldCollector) + old_unaffiliated_regions * region_size_bytes;
}
if (young_reserve_result > young_unaffiliated_regions * region_size_bytes) {
young_reserve_result = young_unaffiliated_regions * region_size_bytes;
}
}
// Having placed all regions that have allocation capacity into the mutator set if they identify as is_young()
// or into the old collector set if they identify as is_old(), move some of these regions from the mutator set
// into the collector set or old collector set in order to assure that the memory available for allocations within
// the collector set is at least to_reserve and the memory available for allocations within the old collector set
// is at least to_reserve_old.
//
// Returns total mutator alloc capacity, in words.
size_t ShenandoahFreeSet::reserve_regions(size_t to_reserve, size_t to_reserve_old, size_t &old_region_count,
size_t &young_used_regions, size_t &old_used_regions,
size_t &young_used_bytes, size_t &old_used_bytes) {
const size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
size_t mutator_allocatable_words = _prepare_to_rebuild_mutator_free;
young_used_regions = 0;
old_used_regions = 0;
young_used_bytes = 0;
old_used_bytes = 0;
idx_t mutator_low_idx = _partitions.max();
idx_t mutator_high_idx = -1;
idx_t mutator_empty_low_idx = _partitions.max();
idx_t mutator_empty_high_idx = -1;
idx_t collector_low_idx = _partitions.max();
idx_t collector_high_idx = -1;
idx_t collector_empty_low_idx = _partitions.max();
idx_t collector_empty_high_idx = -1;
idx_t old_collector_low_idx = _partitions.max();
idx_t old_collector_high_idx = -1;
idx_t old_collector_empty_low_idx = _partitions.max();
idx_t old_collector_empty_high_idx = -1;
size_t used_to_collector = 0;
size_t used_to_old_collector = 0;
size_t regions_to_collector = 0;
size_t regions_to_old_collector = 0;
size_t empty_regions_to_collector = 0;
size_t empty_regions_to_old_collector = 0;
size_t old_collector_available = _partitions.available_in(ShenandoahFreeSetPartitionId::OldCollector);;
size_t collector_available = _partitions.available_in(ShenandoahFreeSetPartitionId::Collector);
for (size_t i = _heap->num_regions(); i > 0; i--) {
idx_t idx = i - 1;
ShenandoahHeapRegion* r = _heap->get_region(idx);
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, idx)) {
// Note: trashed regions have region_size_bytes alloc capacity.
size_t ac = alloc_capacity(r);
assert (ac > 0, "Membership in free set implies has capacity");
assert (!r->is_old() || r->is_trash(), "Except for trash, mutator_is_free regions should not be affiliated OLD");
bool move_to_old_collector = old_collector_available < to_reserve_old;
bool move_to_collector = collector_available < to_reserve;
if (move_to_old_collector) {
// We give priority to OldCollector partition because we desire to pack OldCollector regions into higher
// addresses than Collector regions. Presumably, OldCollector regions are more "stable" and less likely to
// be collected in the near future.
if (r->is_trash() || !r->is_affiliated()) {
// OLD regions that have available memory are already in the old_collector free set.
assert(r->is_empty() || r->is_trash(), "Not affiliated implies region %zu is empty", r->index());
if (idx < old_collector_low_idx) {
old_collector_low_idx = idx;
}
if (idx > old_collector_high_idx) {
old_collector_high_idx = idx;
}
if (idx < old_collector_empty_low_idx) {
old_collector_empty_low_idx = idx;
}
if (idx > old_collector_empty_high_idx) {
old_collector_empty_high_idx = idx;
}
used_to_old_collector +=
_partitions.move_from_partition_to_partition_with_deferred_accounting(idx, ShenandoahFreeSetPartitionId::Mutator,
ShenandoahFreeSetPartitionId::OldCollector, ac);
old_collector_available += ac;
regions_to_old_collector++;
empty_regions_to_old_collector++;
log_trace(gc, free)(" Shifting region %zu from mutator_free to old_collector_free", idx);
log_trace(gc, free)(" Shifted Mutator range [%zd, %zd],"
" Old Collector range [%zd, %zd]",
_partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
_partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector));
old_region_count++;
assert(ac = ShenandoahHeapRegion::region_size_bytes(), "Cannot move to old unless entire region is in alloc capacity");
mutator_allocatable_words -= ShenandoahHeapRegion::region_size_words();
continue;
}
}
if (move_to_collector) {
// Note: In a previous implementation, regions were only placed into the survivor space (collector_is_free) if
// they were entirely empty. This has the effect of causing new Mutator allocation to reside next to objects
// that have already survived at least one GC, mixing ephemeral with longer-lived objects in the same region.
// Any objects that have survived a GC are less likely to immediately become garbage, so a region that contains
// survivor objects is less likely to be selected for the collection set. This alternative implementation allows
// survivor regions to continue accumulating other survivor objects, and makes it more likely that ephemeral objects
// occupy regions comprised entirely of ephemeral objects. These regions are highly likely to be included in the next
// collection set, and they are easily evacuated because they have low density of live objects.
if (idx < collector_low_idx) {
collector_low_idx = idx;
}
if (idx > collector_high_idx) {
collector_high_idx = idx;
}
if (ac == region_size_bytes) {
if (idx < collector_empty_low_idx) {
collector_empty_low_idx = idx;
}
if (idx > collector_empty_high_idx) {
collector_empty_high_idx = idx;
}
empty_regions_to_collector++;
}
used_to_collector +=
_partitions.move_from_partition_to_partition_with_deferred_accounting(idx, ShenandoahFreeSetPartitionId::Mutator,
ShenandoahFreeSetPartitionId::Collector, ac);
collector_available += ac;
regions_to_collector++;
if (ac != region_size_bytes) {
young_used_regions++;
young_used_bytes = region_size_bytes - ac;
}
log_trace(gc, free)(" Shifting region %zu from mutator_free to collector_free", idx);
log_trace(gc, free)(" Shifted Mutator range [%zd, %zd],"
" Collector range [%zd, %zd]",
_partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
_partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector));
mutator_allocatable_words -= ac / HeapWordSize;
continue;
}
// Mutator region is not moved to Collector or OldCollector. Still, do the accounting.
if (idx < mutator_low_idx) {
mutator_low_idx = idx;
}
if (idx > mutator_high_idx) {
mutator_high_idx = idx;
}
if ((ac == region_size_bytes) && (idx < mutator_empty_low_idx)) {
mutator_empty_low_idx = idx;
}
if ((ac == region_size_bytes) && (idx > mutator_empty_high_idx)) {
mutator_empty_high_idx = idx;
}
if (ac != region_size_bytes) {
young_used_regions++;
young_used_bytes += region_size_bytes - ac;
}
} else {
// Region is not in Mutator partition. Do the accounting.
ShenandoahFreeSetPartitionId p = _partitions.membership(idx);
size_t ac = alloc_capacity(r);
assert(ac != region_size_bytes, "Empty regions should be in Mutator partion at entry to reserve_regions");
assert(p != ShenandoahFreeSetPartitionId::Collector, "Collector regions must be converted from Mutator regions");
if (p == ShenandoahFreeSetPartitionId::OldCollector) {
assert(!r->is_empty(), "Empty regions should be in Mutator partition at entry to reserve_regions");
old_used_regions++;
old_used_bytes = region_size_bytes - ac;
// This region is within the range for OldCollector partition, as established by find_regions_with_alloc_capacity()
assert((_partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector) <= idx) &&
(_partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector) >= idx),
"find_regions_with_alloc_capacity() should have established this is in range");
} else {
assert(p == ShenandoahFreeSetPartitionId::NotFree, "sanity");
// This region has been retired
if (r->is_old()) {
old_used_regions++;
old_used_bytes += region_size_bytes - ac;
} else {
assert(r->is_young(), "Retired region should be old or young");
young_used_regions++;
young_used_bytes += region_size_bytes - ac;
}
}
}
}
_partitions.decrease_used(ShenandoahFreeSetPartitionId::Mutator, used_to_old_collector + used_to_collector);
_partitions.decrease_region_counts(ShenandoahFreeSetPartitionId::Mutator, regions_to_old_collector + regions_to_collector);
_partitions.decrease_empty_region_counts(ShenandoahFreeSetPartitionId::Mutator,
empty_regions_to_old_collector + empty_regions_to_collector);
// decrease_capacity() also decreases available
_partitions.decrease_capacity(ShenandoahFreeSetPartitionId::Mutator,
(regions_to_old_collector + regions_to_collector) * region_size_bytes);
// increase_capacity() also increases available
_partitions.increase_capacity(ShenandoahFreeSetPartitionId::Collector, regions_to_collector * region_size_bytes);
_partitions.increase_region_counts(ShenandoahFreeSetPartitionId::Collector, regions_to_collector);
_partitions.increase_empty_region_counts(ShenandoahFreeSetPartitionId::Collector, empty_regions_to_collector);
// increase_capacity() also increases available
_partitions.increase_capacity(ShenandoahFreeSetPartitionId::OldCollector, regions_to_old_collector * region_size_bytes);
_partitions.increase_region_counts(ShenandoahFreeSetPartitionId::OldCollector, regions_to_old_collector);
_partitions.increase_empty_region_counts(ShenandoahFreeSetPartitionId::OldCollector, empty_regions_to_old_collector);
if (used_to_collector > 0) {
_partitions.increase_used(ShenandoahFreeSetPartitionId::Collector, used_to_collector);
}
if (used_to_old_collector > 0) {
_partitions.increase_used(ShenandoahFreeSetPartitionId::OldCollector, used_to_old_collector);
}
_partitions.establish_interval(ShenandoahFreeSetPartitionId::Mutator,
mutator_low_idx, mutator_high_idx, mutator_empty_low_idx, mutator_empty_high_idx);
_partitions.establish_interval(ShenandoahFreeSetPartitionId::Collector,
collector_low_idx, collector_high_idx, collector_empty_low_idx, collector_empty_high_idx);
_partitions.expand_interval_if_range_modifies_either_boundary(ShenandoahFreeSetPartitionId::OldCollector,
old_collector_low_idx, old_collector_high_idx,
old_collector_empty_low_idx, old_collector_empty_high_idx);
recompute_total_used</* UsedByMutatorChanged */ true,
/* UsedByCollectorChanged */ true, /* UsedByOldCollectorChanged */ true>();
recompute_total_affiliated</* MutatorEmptiesChanged */ true, /* CollecteorEmptiesChanged */true,
/* OldCollectorEmptiesChanged */ true, /* MutatorSizeChanged */ true,
/* CollectorSizeChanged */ true, /* OldCollectorSizeChanged */ true,
/* AffiliatedChangesAreYoungNeutral */ false, /* AffiliatedChangesAreGlobalNeutral */ false,
/* UnaffiliatedChangesAreYoungNeutral */ false>();
_partitions.assert_bounds();
if (LogTarget(Info, gc, free)::is_enabled()) {
size_t old_reserve = _partitions.available_in(ShenandoahFreeSetPartitionId::OldCollector);
if (old_reserve < to_reserve_old) {
log_info(gc, free)("Wanted " PROPERFMT " for old reserve, but only reserved: " PROPERFMT,
PROPERFMTARGS(to_reserve_old), PROPERFMTARGS(old_reserve));
assert(_heap->mode()->is_generational(), "to_old_reserve > 0 implies generational mode");
reduce_old_reserve(old_reserve, to_reserve_old);
}
size_t reserve = _partitions.available_in(ShenandoahFreeSetPartitionId::Collector);
if (reserve < to_reserve) {
if (_heap->mode()->is_generational()) {
reduce_young_reserve(reserve, to_reserve);
}
log_info(gc, free)("Wanted " PROPERFMT " for young reserve, but only reserved: " PROPERFMT,
PROPERFMTARGS(to_reserve), PROPERFMTARGS(reserve));
}
}
return mutator_allocatable_words;
}
void ShenandoahFreeSet::establish_old_collector_alloc_bias() {
ShenandoahHeap* heap = ShenandoahHeap::heap();
shenandoah_assert_heaplocked();
idx_t left_idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector);
idx_t right_idx = _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector);
idx_t middle = (left_idx + right_idx) / 2;
size_t available_in_first_half = 0;
size_t available_in_second_half = 0;
for (idx_t index = left_idx; index < middle; index++) {
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, index)) {
ShenandoahHeapRegion* r = heap->get_region((size_t) index);
available_in_first_half += r->free();
}
}
for (idx_t index = middle; index <= right_idx; index++) {
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, index)) {
ShenandoahHeapRegion* r = heap->get_region(index);
available_in_second_half += r->free();
}
}
// We desire to first consume the sparsely distributed regions in order that the remaining regions are densely packed.
// Densely packing regions reduces the effort to search for a region that has sufficient memory to satisfy a new allocation
// request. Regions become sparsely distributed following a Full GC, which tends to slide all regions to the front of the
// heap rather than allowing survivor regions to remain at the high end of the heap where we intend for them to congregate.
_partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::OldCollector,
(available_in_second_half > available_in_first_half));
}
void ShenandoahFreeSet::log_status_under_lock() {
// Must not be heap locked, it acquires heap lock only when log is enabled
shenandoah_assert_not_heaplocked();
if (LogTarget(Info, gc, free)::is_enabled()
DEBUG_ONLY(|| LogTarget(Debug, gc, free)::is_enabled())) {
ShenandoahHeapLocker locker(_heap->lock());
log_status();
}
}
void ShenandoahFreeSet::log_freeset_stats(ShenandoahFreeSetPartitionId partition_id, LogStream& ls) {
size_t max = 0;
size_t total_free = 0;
size_t total_used = 0;
for (idx_t idx = _partitions.leftmost(partition_id);
idx <= _partitions.rightmost(partition_id); idx++) {
if (_partitions.in_free_set(partition_id, idx)) {
ShenandoahHeapRegion *r = _heap->get_region(idx);
size_t free = alloc_capacity(r);
max = MAX2(max, free);
total_free += free;
total_used += r->used();
}
}
ls.print(" %s freeset stats: Partition count: %zu, Reserved: " PROPERFMT ", Max free available in a single region: " PROPERFMT ";",
partition_name(partition_id),
_partitions.count(partition_id),
PROPERFMTARGS(total_free), PROPERFMTARGS(max)
);
}
void ShenandoahFreeSet::log_status() {
shenandoah_assert_heaplocked();
#ifdef ASSERT
// Dump of the FreeSet details is only enabled if assertions are enabled
LogTarget(Debug, gc, free) debug_free;
if (debug_free.is_enabled()) {
#define BUFFER_SIZE 80
LogStream ls(debug_free);
char buffer[BUFFER_SIZE];
for (uint i = 0; i < BUFFER_SIZE; i++) {
buffer[i] = '\0';
}
ls.cr();
ls.print_cr("Mutator free range [%zd..%zd] allocating from %s",
_partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::Mutator)? "left to right": "right to left");
ls.print_cr("Collector free range [%zd..%zd] allocating from %s",
_partitions.leftmost(ShenandoahFreeSetPartitionId::Collector),
_partitions.rightmost(ShenandoahFreeSetPartitionId::Collector),
_partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::Collector)? "left to right": "right to left");
ls.print_cr("Old collector free range [%zd..%zd] allocates from %s",
_partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
_partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector),
_partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::OldCollector)? "left to right": "right to left");
ls.cr();
ls.print_cr("FreeSet map legend:");
ls.print_cr(" M/m:mutator, C/c:collector O/o:old_collector (Empty/Occupied)");
ls.print_cr(" H/h:humongous, X/x:no alloc capacity, ~/_:retired (Old/Young)");
for (uint i = 0; i < _heap->num_regions(); i++) {
ShenandoahHeapRegion *r = _heap->get_region(i);
uint idx = i % 64;
if ((i != 0) && (idx == 0)) {
ls.print_cr(" %6u: %s", i-64, buffer);
}
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, i)) {
size_t capacity = alloc_capacity(r);
assert(!r->is_old() || r->is_trash(), "Old regions except trash regions should not be in mutator_free set");
buffer[idx] = (capacity == ShenandoahHeapRegion::region_size_bytes()) ? 'M' : 'm';
} else if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Collector, i)) {
size_t capacity = alloc_capacity(r);
assert(!r->is_old() || r->is_trash(), "Old regions except trash regions should not be in collector_free set");
buffer[idx] = (capacity == ShenandoahHeapRegion::region_size_bytes()) ? 'C' : 'c';
} else if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, i)) {
size_t capacity = alloc_capacity(r);
buffer[idx] = (capacity == ShenandoahHeapRegion::region_size_bytes()) ? 'O' : 'o';
} else if (r->is_humongous()) {
buffer[idx] = (r->is_old() ? 'H' : 'h');
} else if (alloc_capacity(r) == 0) {
buffer[idx] = (r->is_old() ? 'X' : 'x');
} else {
buffer[idx] = (r->is_old() ? '~' : '_');
}
}
uint remnant = _heap->num_regions() % 64;
if (remnant > 0) {
buffer[remnant] = '\0';
} else {
remnant = 64;
}
ls.print_cr(" %6u: %s", (uint) (_heap->num_regions() - remnant), buffer);
}
#endif
LogTarget(Info, gc, free) lt;
if (lt.is_enabled()) {
ResourceMark rm;
LogStream ls(lt);
{
idx_t last_idx = 0;
size_t max = 0;
size_t max_contig = 0;
size_t empty_contig = 0;
size_t total_used = 0;
size_t total_free = 0;
size_t total_free_ext = 0;
for (idx_t idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator);
idx <= _partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator); idx++) {
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, idx)) {
ShenandoahHeapRegion *r = _heap->get_region(idx);
size_t free = alloc_capacity(r);
max = MAX2(max, free);
size_t used_in_region = r->used();
if (r->is_empty() || r->is_trash()) {
used_in_region = 0;
total_free_ext += free;
if (last_idx + 1 == idx) {
empty_contig++;
} else {
empty_contig = 1;
}
} else {
empty_contig = 0;
}
total_used += used_in_region;
total_free += free;
max_contig = MAX2(max_contig, empty_contig);
last_idx = idx;
}
}
size_t max_humongous = max_contig * ShenandoahHeapRegion::region_size_bytes();
// capacity() is capacity of mutator
// used() is used of mutator
size_t free = capacity_holding_lock() - used_holding_lock();
// Since certain regions that belonged to the Mutator free partition at the time of most recent rebuild may have been
// retired, the sum of used and capacities within regions that are still in the Mutator free partition may not match
// my internally tracked values of used() and free().
assert(free == total_free, "Free memory (%zu) should match calculated memory (%zu)", free, total_free);
ls.print("Whole heap stats: Total free: " PROPERFMT ", Total used: " PROPERFMT ", Max free in a single region: " PROPERFMT
", Max humongous: " PROPERFMT "; ",
PROPERFMTARGS(total_free), PROPERFMTARGS(total_used), PROPERFMTARGS(max), PROPERFMTARGS(max_humongous));
ls.print("Frag stats: ");
size_t frag_ext;
if (total_free_ext > 0) {
frag_ext = 100 - (100 * max_humongous / total_free_ext);
} else {
frag_ext = 0;
}
ls.print("External: %zu%%, ", frag_ext);
size_t frag_int;
if (_partitions.count(ShenandoahFreeSetPartitionId::Mutator) > 0) {
frag_int = (100 * (total_used / _partitions.count(ShenandoahFreeSetPartitionId::Mutator))
/ ShenandoahHeapRegion::region_size_bytes());
} else {
frag_int = 0;
}
ls.print("Internal: %zu%%; ", frag_int);
}
log_freeset_stats(ShenandoahFreeSetPartitionId::Mutator, ls);
log_freeset_stats(ShenandoahFreeSetPartitionId::Collector, ls);
if (_heap->mode()->is_generational()) {
log_freeset_stats(ShenandoahFreeSetPartitionId::OldCollector, ls);
}
}
}
void ShenandoahFreeSet::decrease_humongous_waste_for_regular_bypass(ShenandoahHeapRegion*r, size_t waste) {
shenandoah_assert_heaplocked();
assert(_partitions.membership(r->index()) == ShenandoahFreeSetPartitionId::NotFree, "Humongous regions should be NotFree");
ShenandoahFreeSetPartitionId p =
r->is_old()? ShenandoahFreeSetPartitionId::OldCollector: ShenandoahFreeSetPartitionId::Mutator;
_partitions.decrease_humongous_waste(p, waste);
if (waste >= PLAB::min_size() * HeapWordSize) {
_partitions.decrease_used(p, waste);
_partitions.unretire_to_partition(r, p);
if (r->is_old()) {
recompute_total_used</* UsedByMutatorChanged */ false,
/* UsedByCollectorChanged */ false, /* UsedByOldCollectorChanged */ true>();
} else {
recompute_total_used</* UsedByMutatorChanged */ true,
/* UsedByCollectorChanged */ false, /* UsedByOldCollectorChanged */ false>();
}
}
_total_humongous_waste -= waste;
}
HeapWord* ShenandoahFreeSet::allocate(ShenandoahAllocRequest& req, bool& in_new_region) {
shenandoah_assert_heaplocked();
if (ShenandoahHeapRegion::requires_humongous(req.size())) {
switch (req.type()) {
case ShenandoahAllocRequest::_alloc_shared:
case ShenandoahAllocRequest::_alloc_shared_gc:
in_new_region = true;
return allocate_contiguous(req, /* is_humongous = */ true);
case ShenandoahAllocRequest::_alloc_cds:
in_new_region = true;
return allocate_contiguous(req, /* is_humongous = */ false);
case ShenandoahAllocRequest::_alloc_plab:
case ShenandoahAllocRequest::_alloc_gclab:
case ShenandoahAllocRequest::_alloc_tlab:
in_new_region = false;
assert(false, "Trying to allocate TLAB in humongous region: %zu", req.size());
return nullptr;
default:
ShouldNotReachHere();
return nullptr;
}
} else {
return allocate_single(req, in_new_region);
}
}
void ShenandoahFreeSet::print_on(outputStream* out) const {
out->print_cr("Mutator Free Set: %zu", _partitions.count(ShenandoahFreeSetPartitionId::Mutator));
ShenandoahLeftRightIterator mutator(const_cast<ShenandoahRegionPartitions*>(&_partitions), ShenandoahFreeSetPartitionId::Mutator);
for (idx_t index = mutator.current(); mutator.has_next(); index = mutator.next()) {
_heap->get_region(index)->print_on(out);
}
out->print_cr("Collector Free Set: %zu", _partitions.count(ShenandoahFreeSetPartitionId::Collector));
ShenandoahLeftRightIterator collector(const_cast<ShenandoahRegionPartitions*>(&_partitions), ShenandoahFreeSetPartitionId::Collector);
for (idx_t index = collector.current(); collector.has_next(); index = collector.next()) {
_heap->get_region(index)->print_on(out);
}
if (_heap->mode()->is_generational()) {
out->print_cr("Old Collector Free Set: %zu", _partitions.count(ShenandoahFreeSetPartitionId::OldCollector));
for (idx_t index = _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector);
index <= _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector); index++) {
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, index)) {
_heap->get_region(index)->print_on(out);
}
}
}
}
double ShenandoahFreeSet::internal_fragmentation() {
double squared = 0;
double linear = 0;
ShenandoahLeftRightIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
for (idx_t index = iterator.current(); iterator.has_next(); index = iterator.next()) {
ShenandoahHeapRegion* r = _heap->get_region(index);
size_t used = r->used();
squared += used * used;
linear += used;
}
if (linear > 0) {
double s = squared / (ShenandoahHeapRegion::region_size_bytes() * linear);
return 1 - s;
} else {
return 0;
}
}
double ShenandoahFreeSet::external_fragmentation() {
idx_t last_idx = 0;
size_t max_contig = 0;
size_t empty_contig = 0;
size_t free = 0;
ShenandoahLeftRightIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
for (idx_t index = iterator.current(); iterator.has_next(); index = iterator.next()) {
ShenandoahHeapRegion* r = _heap->get_region(index);
if (r->is_empty()) {
free += ShenandoahHeapRegion::region_size_bytes();
if (last_idx + 1 == index) {
empty_contig++;
} else {
empty_contig = 1;
}
} else {
empty_contig = 0;
}
max_contig = MAX2(max_contig, empty_contig);
last_idx = index;
}
if (free > 0) {
return 1 - (1.0 * max_contig * ShenandoahHeapRegion::region_size_bytes() / free);
} else {
return 0;
}
}
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