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6807801: CMS: could save/restore fewer header words during scavenge

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Age bits need not enter the mark-word preservation calculus; also affected, in addition to CMS, per CR synopsis above, were ParNew (but not DefNew), ParallelScavenge and G1, albeit to a lesser degree than CMS.

Reviewed-by: tonyp, johnc
This commit is contained in:
Y. Srinivas Ramakrishna 2010-12-17 23:41:31 -08:00
parent b2fa4708ad
commit 41bf31bff4
6 changed files with 37 additions and 21 deletions
Download patch file Download diff file Expand all files Collapse all files

7
hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp
View file

@ -3958,8 +3958,6 @@ void G1CollectedHeap::remove_self_forwarding_pointers() {
// Now restore saved marks, if any.
if (_objs_with_preserved_marks != NULL) {
assert(_preserved_marks_of_objs != NULL, "Both or none.");
assert(_objs_with_preserved_marks->length() ==
_preserved_marks_of_objs->length(), "Both or none.");
guarantee(_objs_with_preserved_marks->length() ==
_preserved_marks_of_objs->length(), "Both or none.");
for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
@ -4054,7 +4052,10 @@ void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
}
void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
if (m != markOopDesc::prototype()) {
assert(evacuation_failed(), "Oversaving!");
// We want to call the "for_promotion_failure" version only in the
// case of a promotion failure.
if (m->must_be_preserved_for_promotion_failure(obj)) {
if (_objs_with_preserved_marks == NULL) {
assert(_preserved_marks_of_objs == NULL, "Both or none.");
_objs_with_preserved_marks =

7
hotspot/src/share/vm/gc_implementation/parNew/parNewGeneration.cpp
View file

@ -1058,10 +1058,11 @@ bool ParNewGeneration::is_legal_forward_ptr(oop p) {
#endif
void ParNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
if ((m != markOopDesc::prototype()) &&
(!UseBiasedLocking || (m != markOopDesc::biased_locking_prototype()))) {
if (m->must_be_preserved_for_promotion_failure(obj)) {
// We should really have separate per-worker stacks, rather
// than use locking of a common pair of stacks.
MutexLocker ml(ParGCRareEvent_lock);
DefNewGeneration::preserve_mark_if_necessary(obj, m);
preserve_mark(obj, m);
}
}

2
hotspot/src/share/vm/gc_implementation/parallelScavenge/psScavenge.cpp
View file

@ -694,6 +694,8 @@ void PSScavenge::clean_up_failed_promotion() {
void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
_promotion_failed = true;
if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
// Should use per-worker private stakcs hetre rather than
// locking a common pair of stacks.
ThreadCritical tc;
_preserved_oop_stack.push(obj);
_preserved_mark_stack.push(obj_mark);

17
hotspot/src/share/vm/memory/defNewGeneration.cpp
View file

@ -684,23 +684,28 @@ void DefNewGeneration::remove_forwarding_pointers() {
_preserved_marks_of_objs.clear(true);
}
void DefNewGeneration::preserve_mark(oop obj, markOop m) {
assert(promotion_failed() && m->must_be_preserved_for_promotion_failure(obj),
"Oversaving!");
_objs_with_preserved_marks.push(obj);
_preserved_marks_of_objs.push(m);
}
void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
if (m->must_be_preserved_for_promotion_failure(obj)) {
_objs_with_preserved_marks.push(obj);
_preserved_marks_of_objs.push(m);
preserve_mark(obj, m);
}
}
void DefNewGeneration::handle_promotion_failure(oop old) {
preserve_mark_if_necessary(old, old->mark());
if (!_promotion_failed && PrintPromotionFailure) {
if (PrintPromotionFailure && !_promotion_failed) {
gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ",
old->size());
}
_promotion_failed = true;
preserve_mark_if_necessary(old, old->mark());
// forward to self
old->forward_to(old);
_promotion_failed = true;
_promo_failure_scan_stack.push(old);

1
hotspot/src/share/vm/memory/defNewGeneration.hpp
View file

@ -85,6 +85,7 @@ protected:
// Preserve the mark of "obj", if necessary, in preparation for its mark
// word being overwritten with a self-forwarding-pointer.
void preserve_mark_if_necessary(oop obj, markOop m);
void preserve_mark(oop obj, markOop m); // work routine used by the above
// Together, these keep <object with a preserved mark, mark value> pairs.
// They should always contain the same number of elements.

24
hotspot/src/share/vm/oops/markOop.inline.hpp
View file

@ -30,7 +30,7 @@
#include "oops/markOop.hpp"
#include "runtime/globals.hpp"
// Should this header be preserved during GC?
// Should this header be preserved during GC (when biased locking is enabled)?
inline bool markOopDesc::must_be_preserved_with_bias(oop obj_containing_mark) const {
assert(UseBiasedLocking, "unexpected");
if (has_bias_pattern()) {
@ -47,14 +47,15 @@ inline bool markOopDesc::must_be_preserved_with_bias(oop obj_containing_mark) co
return (!is_unlocked() || !has_no_hash());
}
// Should this header be preserved during GC?
inline bool markOopDesc::must_be_preserved(oop obj_containing_mark) const {
if (!UseBiasedLocking)
return (!is_unlocked() || !has_no_hash());
return must_be_preserved_with_bias(obj_containing_mark);
}
// Should this header (including its age bits) be preserved in the
// case of a promotion failure during scavenge?
// Should this header be preserved in the case of a promotion failure
// during scavenge (when biased locking is enabled)?
inline bool markOopDesc::must_be_preserved_with_bias_for_promotion_failure(oop obj_containing_mark) const {
assert(UseBiasedLocking, "unexpected");
// We don't explicitly save off the mark words of biased and
@ -70,18 +71,20 @@ inline bool markOopDesc::must_be_preserved_with_bias_for_promotion_failure(oop o
prototype_for_object(obj_containing_mark)->has_bias_pattern()) {
return true;
}
return (this != prototype());
return (!is_unlocked() || !has_no_hash());
}
// Should this header be preserved in the case of a promotion failure
// during scavenge?
inline bool markOopDesc::must_be_preserved_for_promotion_failure(oop obj_containing_mark) const {
if (!UseBiasedLocking)
return (this != prototype());
return (!is_unlocked() || !has_no_hash());
return must_be_preserved_with_bias_for_promotion_failure(obj_containing_mark);
}
// Should this header (including its age bits) be preserved in the
// case of a scavenge in which CMS is the old generation?
// Same as must_be_preserved_with_bias_for_promotion_failure() except that
// it takes a klassOop argument, instead of the object of which this is the mark word.
inline bool markOopDesc::must_be_preserved_with_bias_for_cms_scavenge(klassOop klass_of_obj_containing_mark) const {
assert(UseBiasedLocking, "unexpected");
// CMS scavenges preserve mark words in similar fashion to promotion failures; see above
@ -89,11 +92,14 @@ inline bool markOopDesc::must_be_preserved_with_bias_for_cms_scavenge(klassOop k
klass_of_obj_containing_mark->klass_part()->prototype_header()->has_bias_pattern()) {
return true;
}
return (this != prototype());
return (!is_unlocked() || !has_no_hash());
}
// Same as must_be_preserved_for_promotion_failure() except that
// it takes a klassOop argument, instead of the object of which this is the mark word.
inline bool markOopDesc::must_be_preserved_for_cms_scavenge(klassOop klass_of_obj_containing_mark) const {
if (!UseBiasedLocking)
return (this != prototype());
return (!is_unlocked() || !has_no_hash());
return must_be_preserved_with_bias_for_cms_scavenge(klass_of_obj_containing_mark);
}