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8064473: Improved handling of age during object copy in G1

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Reviewed-by: brutisso, tschatzl
This commit is contained in:
Staffan Friberg 2014-11-14 15:03:39 +01:00
parent 4feb7b4dab
commit 04bdb774e1
5 changed files with 28 additions and 31 deletions
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38
hotspot/src/share/vm/gc_implementation/g1/g1ParScanThreadState.cpp
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@ -150,7 +150,8 @@ void G1ParScanThreadState::trim_queue() {
} while (!_refs->is_empty());
}
oop G1ParScanThreadState::copy_to_survivor_space(oop const old) {
oop G1ParScanThreadState::copy_to_survivor_space(oop const old,
markOop const old_mark) {
size_t word_sz = old->size();
HeapRegion* from_region = _g1h->heap_region_containing_raw(old);
// +1 to make the -1 indexes valid...
@ -158,9 +159,8 @@ oop G1ParScanThreadState::copy_to_survivor_space(oop const old) {
assert( (from_region->is_young() && young_index > 0) ||
(!from_region->is_young() && young_index == 0), "invariant" );
G1CollectorPolicy* g1p = _g1h->g1_policy();
markOop m = old->mark();
int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
: m->age();
uint age = old_mark->has_displaced_mark_helper() ? old_mark->displaced_mark_helper()->age()
: old_mark->age();
GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
word_sz);
AllocationContext_t context = from_region->allocation_context();
@ -196,30 +196,22 @@ oop G1ParScanThreadState::copy_to_survivor_space(oop const old) {
alloc_purpose = to_region->is_young() ? GCAllocForSurvived : GCAllocForTenured;
if (g1p->track_object_age(alloc_purpose)) {
// We could simply do obj->incr_age(). However, this causes a
// performance issue. obj->incr_age() will first check whether
// the object has a displaced mark by checking its mark word;
// getting the mark word from the new location of the object
// stalls. So, given that we already have the mark word and we
// are about to install it anyway, it's better to increase the
// age on the mark word, when the object does not have a
// displaced mark word. We're not expecting many objects to have
// a displaced marked word, so that case is not optimized
// further (it could be...) and we simply call obj->incr_age().
if (m->has_displaced_mark_helper()) {
// in this case, we have to install the mark word first,
if (age < markOopDesc::max_age) {
age++;
}
if (old_mark->has_displaced_mark_helper()) {
// In this case, we have to install the mark word first,
// otherwise obj looks to be forwarded (the old mark word,
// which contains the forward pointer, was copied)
obj->set_mark(m);
obj->incr_age();
obj->set_mark(old_mark);
markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
old_mark->set_displaced_mark_helper(new_mark);
} else {
m = m->incr_age();
obj->set_mark(m);
obj->set_mark(old_mark->set_age(age));
}
age_table()->add(obj, word_sz);
age_table()->add(age, word_sz);
} else {
obj->set_mark(m);
obj->set_mark(old_mark);
}
if (G1StringDedup::is_enabled()) {