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8272327: Shenandoah: Avoid enqueuing duplicate string candidates

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Reviewed-by: rkennke
This commit is contained in:
Zhengyu Gu 2021-08-17 00:35:18 +00:00
parent 3fb19279da
commit ee8bf10d32
3 changed files with 10 additions and 2 deletions

4
src/hotspot/share/gc/shenandoah/shenandoahMark.inline.hpp

@ -261,7 +261,9 @@ inline void ShenandoahMark::mark_through_ref(T* p, ShenandoahObjToScanQueue* q,
if ((STRING_DEDUP == ENQUEUE_DEDUP) && ShenandoahStringDedup::is_candidate(obj)) { if ((STRING_DEDUP == ENQUEUE_DEDUP) && ShenandoahStringDedup::is_candidate(obj)) {
assert(ShenandoahStringDedup::is_enabled(), "Must be enabled"); assert(ShenandoahStringDedup::is_enabled(), "Must be enabled");
req->add(obj); req->add(obj);
} else if ((STRING_DEDUP == ALWAYS_DEDUP) && ShenandoahStringDedup::is_string_candidate(obj)) { } else if ((STRING_DEDUP == ALWAYS_DEDUP) &&
ShenandoahStringDedup::is_string_candidate(obj) &&
!ShenandoahStringDedup::dedup_requested(obj)) {
assert(ShenandoahStringDedup::is_enabled(), "Must be enabled"); assert(ShenandoahStringDedup::is_enabled(), "Must be enabled");
req->add(obj); req->add(obj);
} }

1
src/hotspot/share/gc/shenandoah/shenandoahStringDedup.hpp

@ -31,6 +31,7 @@ class ShenandoahStringDedup : public StringDedup {
public: public:
static inline bool is_string_candidate(oop obj); static inline bool is_string_candidate(oop obj);
static inline bool is_candidate(oop obj); static inline bool is_candidate(oop obj);
static inline bool dedup_requested(oop obj);
}; };
#endif // SHARE_GC_SHENANDOAH_SHENANDOAHSTRINGDEDUP_HPP #endif // SHARE_GC_SHENANDOAH_SHENANDOAHSTRINGDEDUP_HPP

7
src/hotspot/share/gc/shenandoah/shenandoahStringDedup.inline.hpp

@ -36,6 +36,10 @@ bool ShenandoahStringDedup::is_string_candidate(oop obj) {
java_lang_String::value(obj) != nullptr; java_lang_String::value(obj) != nullptr;
} }
bool ShenandoahStringDedup::dedup_requested(oop obj) {
return java_lang_String::test_and_set_deduplication_requested(obj);
}
bool ShenandoahStringDedup::is_candidate(oop obj) { bool ShenandoahStringDedup::is_candidate(oop obj) {
if (!is_string_candidate(obj)) { if (!is_string_candidate(obj)) {
return false; return false;
@ -51,7 +55,8 @@ bool ShenandoahStringDedup::is_candidate(oop obj) {
// Increase string age and enqueue it when it rearches age threshold // Increase string age and enqueue it when it rearches age threshold
markWord new_mark = mark.incr_age(); markWord new_mark = mark.incr_age();
if (mark == obj->cas_set_mark(new_mark, mark)) { if (mark == obj->cas_set_mark(new_mark, mark)) {
return StringDedup::is_threshold_age(new_mark.age()); return StringDedup::is_threshold_age(new_mark.age()) &&
!dedup_requested(obj);
} }
} }
return false; return false;