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8385430: Shenandoah: Compact heuristic runs continuously when allocation is idle

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Reviewed-by: shade, kdnilsen
This commit is contained in:
William Kemper 2026-05-28 17:56:45 +00:00
parent e615d49032
commit 4eb67734b7
2 changed files with 12 additions and 11 deletions
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19
src/hotspot/share/gc/shenandoah/heuristics/shenandoahCompactHeuristics.cpp
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@ -32,7 +32,8 @@
#include "logging/logTag.hpp"
ShenandoahCompactHeuristics::ShenandoahCompactHeuristics(ShenandoahSpaceInfo* space_info) :
ShenandoahHeuristics(space_info) {
ShenandoahHeuristics(space_info),
_bytes_used_at_end_of_gc(0) {
SHENANDOAH_ERGO_ENABLE_FLAG(ExplicitGCInvokesConcurrent);
SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahImplicitGCInvokesConcurrent);
SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahUncommit);
@ -46,9 +47,10 @@ ShenandoahCompactHeuristics::ShenandoahCompactHeuristics(ShenandoahSpaceInfo* sp
}
bool ShenandoahCompactHeuristics::should_start_gc() {
const size_t used = _space_info->used();
const size_t capacity = ShenandoahHeap::heap()->soft_max_capacity();
const size_t available = _space_info->soft_mutator_available();
const size_t bytes_allocated = estimate_bytes_allocated_since_gc_start();
const size_t bytes_allocated = used > _bytes_used_at_end_of_gc ? used - _bytes_used_at_end_of_gc : 0;
log_debug(gc, ergo)("should_start_gc calculation: available: " PROPERFMT ", soft_max_capacity: " PROPERFMT ", "
"allocated_since_gc_start: " PROPERFMT,
@ -74,6 +76,11 @@ bool ShenandoahCompactHeuristics::should_start_gc() {
return ShenandoahHeuristics::should_start_gc();
}
void ShenandoahCompactHeuristics::record_cycle_end() {
ShenandoahHeuristics::record_cycle_end();
_bytes_used_at_end_of_gc = _space_info->used();
}
void ShenandoahCompactHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
RegionData* data, size_t size,
size_t actual_free) {
@ -94,11 +101,3 @@ void ShenandoahCompactHeuristics::choose_collection_set_from_regiondata(Shenando
}
}
}
size_t ShenandoahCompactHeuristics::estimate_bytes_allocated_since_gc_start() const {
ShenandoahHeap* heap = ShenandoahHeap::heap();
const double average_allocation_rate = heap->alloc_rate().weighted_average();
const double now = os::elapsedTime();
const double elapsed_seconds = now - cycle_start_time_seconds();
return shenandoah_safe_size_cast(average_allocation_rate * elapsed_seconds);
}

4
src/hotspot/share/gc/shenandoah/heuristics/shenandoahCompactHeuristics.hpp
View File

@ -41,13 +41,15 @@ public:
bool is_diagnostic() override { return false; }
bool is_experimental() override { return false; }
void record_cycle_end() override;
protected:
void choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
RegionData* data, size_t size,
size_t actual_free) override;
private:
size_t estimate_bytes_allocated_since_gc_start() const;
size_t _bytes_used_at_end_of_gc;
};
#endif // SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHCOMPACTHEURISTICS_HPP