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8371284: GenShen: Avoid unnecessary card marking #28204

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8371284: GenShen: Avoid unnecessary card marking #28204

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47612c0
exclude young-yong, old-old and honor UseCondCardMark in dirty card m…
Nov 7, 2025
fac569b
Merge branch 'openjdk:master' into 8371284
nityarai08 Nov 7, 2025
154a509
minor cleanup
Nov 7, 2025
09ad25a
clean whitespace
Nov 7, 2025
59f7a0d
early return of oop is null
Nov 7, 2025
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22 changes: 21 additions & 1 deletion src/hotspot/share/gc/shenandoah/shenandoahBarrierSet.inline.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -191,8 +191,28 @@ inline void ShenandoahBarrierSet::keep_alive_if_weak(DecoratorSet decorators, oo
template <DecoratorSet decorators, typename T>
inline void ShenandoahBarrierSet::write_ref_field_post(T* field) {
assert(ShenandoahCardBarrier, "Should have been checked by caller");
//Exclude if young field
if (_heap->is_in_young(field)) {
return;
}
T heap_oop = RawAccess<>::oop_load(field);
if (CompressedOops::is_null(heap_oop)) {
return;
}
oop obj = CompressedOops::decode_not_null(heap_oop);
// Field is in old generation, If referenced object is also in old gen, skip card marking
if (!_heap->is_in_young(obj)) {
return;
}
// Honor UseCondCardMark: check if card is already dirty before writing
volatile CardTable::CardValue* byte = card_table()->byte_for(field);
*byte = CardTable::dirty_card_val();
if (UseCondCardMark) {
if (*byte != CardTable::dirty_card_val()) {
*byte = CardTable::dirty_card_val();
}
} else {
*byte = CardTable::dirty_card_val();
}
}

template <typename T>
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