Clear (madvise) card table for CC
Since the cards are not really used, we can madvise them to reduce
RAM. Image and zygote cards are cleared in pause to prevent races
between with mutators.
Pause time goes up by only 1.5us on N6P maps:
(Paused)ClearCards: Sum: 755us 99% C.I. 0.250us-28us Avg: 1.540us Max: 28us
AOSP N6P before (60s after boot system wide CC):
4,194K: .GC
4,172K: .GC
4,110K: .GC
After:
3,253K: .GC
3,205K: .GC
3,245K: .GC
Bug: 12687968
Test: test-art-host
Change-Id: I3194b5b8044c2dca427302c32d9974920fecb289
diff --git a/runtime/gc/collector/concurrent_copying.cc b/runtime/gc/collector/concurrent_copying.cc
index 13af67e..c43b048 100644
--- a/runtime/gc/collector/concurrent_copying.cc
+++ b/runtime/gc/collector/concurrent_copying.cc
@@ -486,9 +486,14 @@
// Table is non null for boot image and zygote spaces. It is only null for application image
// spaces.
if (table != nullptr) {
- // TODO: Add preclean outside the pause.
- table->ClearCards();
+ // TODO: Consider adding precleaning outside the pause.
+ table->ProcessCards();
table->VisitObjects(GrayImmuneObjectVisitor::Callback, &visitor);
+ // Since the cards are recorded in the mod-union table and this is paused, we can clear
+ // the cards for the space (to madvise).
+ TimingLogger::ScopedTiming split2("(Paused)ClearCards", GetTimings());
+ card_table->ClearCardRange(space->Begin(),
+ AlignDown(space->End(), accounting::CardTable::kCardSize));
} else {
// TODO: Consider having a mark bitmap for app image spaces and avoid scanning during the
// pause because app image spaces are all dirty pages anyways.
@@ -2325,9 +2330,14 @@
MutexLock mu(self, mark_stack_lock_);
CHECK_EQ(pooled_mark_stacks_.size(), kMarkStackPoolSize);
}
- region_space_ = nullptr;
{
- MutexLock mu(Thread::Current(), skipped_blocks_lock_);
+ TimingLogger::ScopedTiming split("ClearRegionSpaceCards", GetTimings());
+ // We do not currently use the region space cards at all, madvise them away to save ram.
+ heap_->GetCardTable()->ClearCardRange(region_space_->Begin(), region_space_->Limit());
+ region_space_ = nullptr;
+ }
+ {
+ MutexLock mu(self, skipped_blocks_lock_);
skipped_blocks_map_.clear();
}
{
@@ -2339,10 +2349,9 @@
if (kUseBakerReadBarrier && kFilterModUnionCards) {
TimingLogger::ScopedTiming split("FilterModUnionCards", GetTimings());
ReaderMutexLock mu2(self, *Locks::heap_bitmap_lock_);
- gc::Heap* const heap = Runtime::Current()->GetHeap();
for (space::ContinuousSpace* space : immune_spaces_.GetSpaces()) {
DCHECK(space->IsImageSpace() || space->IsZygoteSpace());
- accounting::ModUnionTable* table = heap->FindModUnionTableFromSpace(space);
+ accounting::ModUnionTable* table = heap_->FindModUnionTableFromSpace(space);
// Filter out cards that don't need to be set.
if (table != nullptr) {
table->FilterCards();
@@ -2351,7 +2360,7 @@
}
if (kUseBakerReadBarrier) {
TimingLogger::ScopedTiming split("EmptyRBMarkBitStack", GetTimings());
- DCHECK(rb_mark_bit_stack_.get() != nullptr);
+ DCHECK(rb_mark_bit_stack_ != nullptr);
const auto* limit = rb_mark_bit_stack_->End();
for (StackReference<mirror::Object>* it = rb_mark_bit_stack_->Begin(); it != limit; ++it) {
CHECK(it->AsMirrorPtr()->AtomicSetMarkBit(1, 0));