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Avoid AtomicAccess::load in attempt_allocation_in_alloc_regions when called from attempt_allocation_slow

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This commit is contained in:
Xiaolong Peng 2026-01-08 15:59:47 -08:00
parent 47d850d3ce
commit 8c99ebee78
2 changed files with 4 additions and 2 deletions
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5
src/hotspot/share/gc/shenandoah/shenandoahAllocator.cpp
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@ -123,7 +123,7 @@ HeapWord* ShenandoahAllocator<ALLOC_PARTITION>::attempt_allocation_slow(Shenando
uint regions_ready_for_refresh = 0u;
// Attempt to allocate in shared alloc regions after taking heap lock,
// because other mutator may have refreshed shared alloc regions
HeapWord* obj = attempt_allocation_in_alloc_regions(req, in_new_region, alloc_start_index(), regions_ready_for_refresh);
HeapWord* obj = attempt_allocation_in_alloc_regions<true /*holding heap lock*/>(req, in_new_region, alloc_start_index(), regions_ready_for_refresh);
if (obj != nullptr) {
return obj;
}
@ -182,6 +182,7 @@ HeapWord* ShenandoahAllocator<ALLOC_PARTITION>::attempt_allocation_from_free_set
}
template <ShenandoahFreeSetPartitionId ALLOC_PARTITION>
template<bool HOLDING_HEAP_LOCK>
HeapWord* ShenandoahAllocator<ALLOC_PARTITION>::attempt_allocation_in_alloc_regions(ShenandoahAllocRequest &req,
bool &in_new_region,
uint const alloc_start_index,
@ -189,7 +190,7 @@ HeapWord* ShenandoahAllocator<ALLOC_PARTITION>::attempt_allocation_in_alloc_regi
assert(regions_ready_for_refresh == 0u && in_new_region == false && alloc_start_index < _alloc_region_count, "Sanity check");
uint i = alloc_start_index;
do {
if (ShenandoahHeapRegion* r = nullptr; (r = AtomicAccess::load(&_alloc_regions[i].address)) != nullptr) {
if (ShenandoahHeapRegion* r = nullptr; (r = HOLDING_HEAP_LOCK ? _alloc_regions[i].address : AtomicAccess::load(&_alloc_regions[i].address)) != nullptr) {
bool ready_for_retire = false;
HeapWord* obj = allocate_in<true>(r, true, req, in_new_region, ready_for_retire);
if (ready_for_retire) {

1
src/hotspot/share/gc/shenandoah/shenandoahAllocator.hpp
View File

@ -71,6 +71,7 @@ protected:
// Attempt to allocate in a shared alloc region using atomic operation without holding the heap lock.
// Returns nullptr and overwrites regions_ready_for_refresh with the number of shared alloc regions that are ready
// to be retired if it is unable to satisfy the allocation request from the existing shared alloc regions.
template<bool HOLDING_HEAP_LOCK = false>
HeapWord* attempt_allocation_in_alloc_regions(ShenandoahAllocRequest& req, bool& in_new_region, uint const alloc_start_index, uint &regions_ready_for_refresh);
// Allocate in a region, use atomic operations if template parameter ATOMIC is true.