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src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp
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rev 7518 : 8048179: Early reclaim of large objects that are referenced by a few objects
Summary:
Reviewed-by:
*** 3482,3538 ****
HeapRegion* region = region_at(index);
assert(region->is_starts_humongous(), "Must start a humongous object");
return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
}
class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
private:
size_t _total_humongous;
size_t _candidate_humongous;
public:
! RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
}
virtual bool doHeapRegion(HeapRegion* r) {
if (!r->is_starts_humongous()) {
return false;
}
G1CollectedHeap* g1h = G1CollectedHeap::heap();
uint region_idx = r->hrm_index();
! bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
! // Is_candidate already filters out humongous regions with some remembered set.
! // This will not lead to humongous object that we mistakenly keep alive because
! // during young collection the remembered sets will only be added to.
if (is_candidate) {
g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
_candidate_humongous++;
}
_total_humongous++;
return false;
}
size_t total_humongous() const { return _total_humongous; }
size_t candidate_humongous() const { return _candidate_humongous; }
};
void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
! g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
return;
}
RegisterHumongousWithInCSetFastTestClosure cl;
heap_region_iterate(&cl);
! g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
cl.candidate_humongous());
_has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
if (_has_humongous_reclaim_candidates || G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
clear_humongous_is_live_table();
}
}
void
G1CollectedHeap::setup_surviving_young_words() {
assert(_surviving_young_words == NULL, "pre-condition");
--- 3482,3578 ----
HeapRegion* region = region_at(index);
assert(region->is_starts_humongous(), "Must start a humongous object");
return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
}
+ bool G1CollectedHeap::humongous_region_is_candidate(uint index) {
+ HeapRegion* region = region_at(index);
+ assert(region->is_starts_humongous(), "Must start a humongous object");
+ return !oop(region->bottom())->is_objArray() &&
+ ((G1ReclaimDeadHumongousObjectsWithRefsAtYoungGC && region->rem_set()->is_small_for_eager_reclaim()) ||
+ (!G1ReclaimDeadHumongousObjectsWithRefsAtYoungGC && region->rem_set()->is_empty()));
+ }
+
class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
private:
size_t _total_humongous;
size_t _candidate_humongous;
+
+ DirtyCardQueue _dcq;
public:
! RegisterHumongousWithInCSetFastTestClosure()
! : _total_humongous(0),
! _candidate_humongous(0),
! _dcq(&JavaThread::dirty_card_queue_set()) {
}
virtual bool doHeapRegion(HeapRegion* r) {
if (!r->is_starts_humongous()) {
return false;
}
G1CollectedHeap* g1h = G1CollectedHeap::heap();
uint region_idx = r->hrm_index();
! bool is_candidate = g1h->humongous_region_is_candidate(region_idx);
! // Is_candidate already filters out humongous object with large remembered sets.
! // If we have a humongous object with a few remembered sets, we simply flush these
! // remembered set entries into the DCQS. That will result in automatic
! // re-evaluation of their remembered set entries during the following evacuation
! // phase.
if (is_candidate) {
+ if (!r->rem_set()->is_empty()) {
+ guarantee(r->rem_set()->is_small_for_eager_reclaim(),
+ "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
+ G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
+ HeapRegionRemSetIterator hrrs(r->rem_set());
+ size_t card_index;
+ while (hrrs.has_next(card_index)) {
+ jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
+ if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
+ *card_ptr = CardTableModRefBS::dirty_card_val();
+ _dcq.enqueue(card_ptr);
+ }
+ }
+ r->rem_set()->clear_locked();
+ }
+ assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
_candidate_humongous++;
}
_total_humongous++;
return false;
}
size_t total_humongous() const { return _total_humongous; }
size_t candidate_humongous() const { return _candidate_humongous; }
+
+ void flush_rem_set_entries() { _dcq.flush(); }
};
void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
! g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
return;
}
+ double time = os::elapsed_counter();
RegisterHumongousWithInCSetFastTestClosure cl;
heap_region_iterate(&cl);
!
! time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
! g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
! cl.total_humongous(),
cl.candidate_humongous());
_has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
if (_has_humongous_reclaim_candidates || G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
clear_humongous_is_live_table();
}
+
+ // Finally flush all remembered set entries to re-check into the global DCQS.
+ cl.flush_rem_set_entries();
}
void
G1CollectedHeap::setup_surviving_young_words() {
assert(_surviving_young_words == NULL, "pre-condition");
*** 6131,6156 ****
// nobody has a reference to it.
// At the start of collection we flush all refinement logs, and remembered sets
// are completely up-to-date wrt to references to the humongous object.
//
// Other implementation considerations:
! // - never consider object arrays: while they are a valid target, they have not
! // been observed to be used as temporary objects.
! // - they would also pose considerable effort for cleaning up the the remembered
! // sets.
! // While this cleanup is not strictly necessary to be done (or done instantly),
! // given that their occurrence is very low, this saves us this additional
! // complexity.
uint region_idx = r->hrm_index();
if (g1h->humongous_is_live(region_idx) ||
g1h->humongous_region_is_always_live(region_idx)) {
if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
! gclog_or_tty->print_cr("Live humongous %d region %d size "SIZE_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
! r->is_humongous(),
region_idx,
obj->size()*HeapWordSize,
r->rem_set()->occupied(),
r->rem_set()->strong_code_roots_list_length(),
next_bitmap->isMarked(r->bottom()),
g1h->humongous_is_live(region_idx),
obj->is_objArray()
--- 6171,6194 ----
// nobody has a reference to it.
// At the start of collection we flush all refinement logs, and remembered sets
// are completely up-to-date wrt to references to the humongous object.
//
// Other implementation considerations:
! // - never consider object arrays at this time because they would pose
! // considerable effort for cleaning up the the remembered sets. This is
! // required because stale remembered sets might reference locations that
! // are currently allocated into.
uint region_idx = r->hrm_index();
if (g1h->humongous_is_live(region_idx) ||
g1h->humongous_region_is_always_live(region_idx)) {
if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
! gclog_or_tty->print_cr("Live humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
region_idx,
obj->size()*HeapWordSize,
+ r->bottom(),
+ r->region_num(),
r->rem_set()->occupied(),
r->rem_set()->strong_code_roots_list_length(),
next_bitmap->isMarked(r->bottom()),
g1h->humongous_is_live(region_idx),
obj->is_objArray()
*** 6163,6177 ****
guarantee(!obj->is_objArray(),
err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
r->bottom()));
if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
! gclog_or_tty->print_cr("Reclaim humongous region %d size "SIZE_FORMAT" start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
! r->is_humongous(),
obj->size()*HeapWordSize,
r->bottom(),
- region_idx,
r->region_num(),
r->rem_set()->occupied(),
r->rem_set()->strong_code_roots_list_length(),
next_bitmap->isMarked(r->bottom()),
g1h->humongous_is_live(region_idx),
--- 6201,6214 ----
guarantee(!obj->is_objArray(),
err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
r->bottom()));
if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
! gclog_or_tty->print_cr("Dead humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
! region_idx,
obj->size()*HeapWordSize,
r->bottom(),
r->region_num(),
r->rem_set()->occupied(),
r->rem_set()->strong_code_roots_list_length(),
next_bitmap->isMarked(r->bottom()),
g1h->humongous_is_live(region_idx),
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