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8204524: Unnecessary memory barriers in G1ParScanThreadState::copy_to_survivor_space

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Reviewed-by: kbarrett, mdoerr, drwhite, tschatzl
This commit is contained in:
Michihiro Horie 2018-06-25 10:41:03 +02:00
parent 84eec7f854
commit 4641ea7bed
3 changed files with 5 additions and 5 deletions
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4
src/hotspot/share/gc/g1/g1ParScanThreadState.cpp
View file

@ -266,7 +266,7 @@ oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes); Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
const oop obj = oop(obj_ptr); const oop obj = oop(obj_ptr);
const oop forward_ptr = old->forward_to_atomic(obj); const oop forward_ptr = old->forward_to_atomic(obj, memory_order_relaxed);
if (forward_ptr == NULL) { if (forward_ptr == NULL) {
Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz); Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
@ -356,7 +356,7 @@ void G1ParScanThreadStateSet::flush() {
oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) { oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
assert(_g1h->is_in_cset(old), "Object " PTR_FORMAT " should be in the CSet", p2i(old)); assert(_g1h->is_in_cset(old), "Object " PTR_FORMAT " should be in the CSet", p2i(old));
oop forward_ptr = old->forward_to_atomic(old); oop forward_ptr = old->forward_to_atomic(old, memory_order_relaxed);
if (forward_ptr == NULL) { if (forward_ptr == NULL) {
// Forward-to-self succeeded. We are the "owner" of the object. // Forward-to-self succeeded. We are the "owner" of the object.
HeapRegion* r = _g1h->heap_region_containing(old); HeapRegion* r = _g1h->heap_region_containing(old);

2
src/hotspot/share/oops/oop.hpp
View file

@ -266,7 +266,7 @@ class oopDesc {
// Exactly one thread succeeds in inserting the forwarding pointer, and // Exactly one thread succeeds in inserting the forwarding pointer, and
// this call returns "NULL" for that thread; any other thread has the // this call returns "NULL" for that thread; any other thread has the
// value of the forwarding pointer returned and does not modify "this". // value of the forwarding pointer returned and does not modify "this".
inline oop forward_to_atomic(oop p); inline oop forward_to_atomic(oop p, atomic_memory_order order = memory_order_conservative);
inline oop forwardee() const; inline oop forwardee() const;
inline oop forwardee_acquire() const; inline oop forwardee_acquire() const;

4
src/hotspot/share/oops/oop.inline.hpp
View file

@ -352,7 +352,7 @@ bool oopDesc::cas_forward_to(oop p, markOop compare, atomic_memory_order order)
return cas_set_mark_raw(m, compare, order) == compare; return cas_set_mark_raw(m, compare, order) == compare;
} }
oop oopDesc::forward_to_atomic(oop p) { oop oopDesc::forward_to_atomic(oop p, atomic_memory_order order) {
markOop oldMark = mark_raw(); markOop oldMark = mark_raw();
markOop forwardPtrMark = markOopDesc::encode_pointer_as_mark(p); markOop forwardPtrMark = markOopDesc::encode_pointer_as_mark(p);
markOop curMark; markOop curMark;
@ -361,7 +361,7 @@ oop oopDesc::forward_to_atomic(oop p) {
assert(sizeof(markOop) == sizeof(intptr_t), "CAS below requires this."); assert(sizeof(markOop) == sizeof(intptr_t), "CAS below requires this.");
while (!oldMark->is_marked()) { while (!oldMark->is_marked()) {
curMark = cas_set_mark_raw(forwardPtrMark, oldMark); curMark = cas_set_mark_raw(forwardPtrMark, oldMark, order);
assert(is_forwarded(), "object should have been forwarded"); assert(is_forwarded(), "object should have been forwarded");
if (curMark == oldMark) { if (curMark == oldMark) {
return NULL; return NULL;