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[heap] Do not shortcut strings when shared marking is active

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We DCHECK in the scavenger that evacuated objects are not allocated
on evacuation candidates. This DCHECK fails however when
shortcutting ThinStrings to the actual string object when
incremental marking is enabled in the shared heap.

We fix this by disabling shortcutting of strings when shared
incremental marking is enabled. We already do this for incremental
marking in the local isolate.

Bug: v8:13267, chromium:1412643
Change-Id: I2a61028ae5377c7621b917ed332e15d6b25b80ff
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4219781
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Auto-Submit: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#85677}
This commit is contained in:
Dominik Inführ 2023-02-06 12:46:15 +01:00 committed by V8 LUCI CQ
parent 088c2c560a
commit f707a4d8f0
2 changed files with 18 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
src/heap/scavenger-inl.h
View File

@ -298,7 +298,7 @@ SlotCallbackResult Scavenger::EvacuateThinString(Map map, THeapObjectSlot slot,
static_assert(std::is_same<THeapObjectSlot, FullHeapObjectSlot>::value ||
std::is_same<THeapObjectSlot, HeapObjectSlot>::value,
"Only FullHeapObjectSlot and HeapObjectSlot are expected here");
if (!is_incremental_marking_ && shortcut_strings_) {
if (shortcut_strings_) {
// The ThinString should die after Scavenge, so avoid writing the proper
// forwarding pointer and instead just signal the actual object as forwarded
// reference.
@ -326,7 +326,7 @@ SlotCallbackResult Scavenger::EvacuateShortcutCandidate(Map map,
"Only FullHeapObjectSlot and HeapObjectSlot are expected here");
DCHECK(IsShortcutCandidate(map.instance_type()));
if (!is_incremental_marking_ && shortcut_strings_ &&
if (shortcut_strings_ &&
object.unchecked_second() == ReadOnlyRoots(heap()).empty_string()) {
HeapObject first = HeapObject::cast(object.unchecked_first());

18
src/heap/scavenger.cc
View File

@ -610,6 +610,18 @@ ConcurrentAllocator* CreateSharedOldAllocator(Heap* heap) {
}
return nullptr;
}
// This returns true if the scavenger runs in a client isolate and incremental
// marking is enabled in the shared space isolate.
bool IsSharedIncrementalMarking(Isolate* isolate) {
return isolate->has_shared_heap() && v8_flags.shared_space &&
!isolate->is_shared_space_isolate() &&
isolate->shared_space_isolate()
->heap()
->incremental_marking()
->IsMarking();
}
} // namespace
Scavenger::Scavenger(ScavengerCollector* collector, Heap* heap, bool is_logging,
@ -633,8 +645,10 @@ Scavenger::Scavenger(ScavengerCollector* collector, Heap* heap, bool is_logging,
is_compacting_(heap->incremental_marking()->IsCompacting()),
shared_string_table_(shared_old_allocator_.get() != nullptr),
mark_shared_heap_(heap->isolate()->is_shared_space_isolate()),
shortcut_strings_(!heap->IsGCWithStack() ||
v8_flags.shortcut_strings_with_stack) {}
shortcut_strings_(
(!heap->IsGCWithStack() || v8_flags.shortcut_strings_with_stack) &&
!is_incremental_marking_ &&
!IsSharedIncrementalMarking(heap->isolate())) {}
void Scavenger::IterateAndScavengePromotedObject(HeapObject target, Map map,
int size) {