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[heap] Update page promotion heuristics

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This CL includes the following changes:
1) Ignore ShouldReduceMemory for MinorMC (since it can't move objects)
2) Make FLAG_page_promotion more explicit in the condition
3) Take wasted bytes into account for MinorMC (full GC can compact and
   "reset" wasted bytes)

Bug: v8:12612
Change-Id: I64d214e692b8ecd20189c59e2a77807f05e43817
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3879606
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83086}
This commit is contained in:
Omer Katz 2022-09-08 11:43:15 +02:00 committed by V8 LUCI CQ
parent 0c793e7073
commit 5767c95604
2 changed files with 17 additions and 10 deletions
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26
src/heap/mark-compact.cc
View File

@ -4150,10 +4150,8 @@ class Evacuator : public Malloced {
// NewSpacePages with more live bytes than this threshold qualify for fast
// evacuation.
static intptr_t NewSpacePageEvacuationThreshold() {
if (v8_flags.page_promotion)
return v8_flags.page_promotion_threshold *
MemoryChunkLayout::AllocatableMemoryInDataPage() / 100;
return MemoryChunkLayout::AllocatableMemoryInDataPage() + kTaggedSize;
return v8_flags.page_promotion_threshold *
MemoryChunkLayout::AllocatableMemoryInDataPage() / 100;
}
Evacuator(Heap* heap, RecordMigratedSlotVisitor* record_visitor,
@ -4469,12 +4467,15 @@ size_t CreateAndExecuteEvacuationTasks(
return wanted_num_tasks;
}
bool ShouldMovePage(Page* p, intptr_t live_bytes,
bool ShouldMovePage(Page* p, intptr_t live_bytes, intptr_t wasted_bytes,
MemoryReductionMode memory_reduction_mode,
AlwaysPromoteYoung always_promote_young) {
Heap* heap = p->heap();
const bool reduce_memory = heap->ShouldReduceMemory();
return !reduce_memory && !p->NeverEvacuate() &&
(live_bytes > Evacuator::NewSpacePageEvacuationThreshold()) &&
return v8_flags.page_promotion &&
(memory_reduction_mode == MemoryReductionMode::kNone) &&
!p->NeverEvacuate() &&
(live_bytes + wasted_bytes >
Evacuator::NewSpacePageEvacuationThreshold()) &&
(always_promote_young == AlwaysPromoteYoung::kYes ||
heap->new_space()->IsPromotionCandidate(p)) &&
heap->CanExpandOldGeneration(live_bytes);
@ -4511,7 +4512,11 @@ void MarkCompactCollector::EvacuatePagesInParallel() {
intptr_t live_bytes_on_page = non_atomic_marking_state()->live_bytes(page);
DCHECK_LT(0, live_bytes_on_page);
live_bytes += live_bytes_on_page;
if (ShouldMovePage(page, live_bytes_on_page, AlwaysPromoteYoung::kYes) ||
MemoryReductionMode memory_reduction_mode =
heap()->ShouldReduceMemory() ? MemoryReductionMode::kShouldReduceMemory
: MemoryReductionMode::kNone;
if (ShouldMovePage(page, live_bytes_on_page, 0, memory_reduction_mode,
AlwaysPromoteYoung::kYes) ||
force_page_promotion) {
EvacuateNewSpacePageVisitor<NEW_TO_OLD>::Move(page);
DCHECK_EQ(heap()->old_space(), page->owner());
@ -6669,7 +6674,8 @@ void MinorMarkCompactCollector::EvacuatePagesInParallel() {
intptr_t live_bytes_on_page = non_atomic_marking_state()->live_bytes(page);
DCHECK_LT(0, live_bytes_on_page);
live_bytes += live_bytes_on_page;
if (ShouldMovePage(page, live_bytes_on_page, AlwaysPromoteYoung::kNo)) {
if (ShouldMovePage(page, live_bytes_on_page, page->wasted_memory(),
MemoryReductionMode::kNone, AlwaysPromoteYoung::kNo)) {
EvacuateNewSpacePageVisitor<NEW_TO_OLD>::Move(page);
evacuation_items.emplace_back(ParallelWorkItem{}, page);
}

1
src/heap/mark-compact.h
View File

@ -173,6 +173,7 @@ class LiveObjectVisitor : AllStatic {
};
enum class AlwaysPromoteYoung { kYes, kNo };
enum class MemoryReductionMode { kNone, kShouldReduceMemory };
enum PageEvacuationMode { NEW_TO_NEW, NEW_TO_OLD };
enum class RememberedSetUpdatingMode { ALL, OLD_TO_NEW_ONLY };