Reduce unnecessary read barriers in GC
Removed read barrier from IsUnprocessed, DequeuePendingReference,
EnqueueReference, and a few other places.
Hard to tell if GC time goes down.
EAAC:
Before GC slow path count: 254857
After GC slow path count: 1005
Bug: 30162165
Bug: 12687968
Test: test-art-host, volantis boot with CC
Change-Id: Ic2add3a9b1e1d7561b0b167f2218b10f8dbff76c
diff --git a/runtime/gc/collector/concurrent_copying.cc b/runtime/gc/collector/concurrent_copying.cc
index d413a50..bd07bb8 100644
--- a/runtime/gc/collector/concurrent_copying.cc
+++ b/runtime/gc/collector/concurrent_copying.cc
@@ -1714,12 +1714,19 @@
// Scan ref fields of an object.
inline void ConcurrentCopying::Scan(mirror::Object* to_ref) {
+ if (kIsDebugBuild) {
+ // Avoid all read barriers during visit references to help performance.
+ Thread::Current()->ModifyDebugDisallowReadBarrier(1);
+ }
DCHECK(!region_space_->IsInFromSpace(to_ref));
DCHECK_EQ(Thread::Current(), thread_running_gc_);
RefFieldsVisitor visitor(this);
// Disable the read barrier for a performance reason.
to_ref->VisitReferences</*kVisitNativeRoots*/true, kDefaultVerifyFlags, kWithoutReadBarrier>(
visitor, visitor);
+ if (kIsDebugBuild) {
+ Thread::Current()->ModifyDebugDisallowReadBarrier(-1);
+ }
}
// Process a field.
@@ -1836,7 +1843,7 @@
mirror::Class* int_array_class = mirror::IntArray::GetArrayClass();
CHECK(int_array_class != nullptr);
AssertToSpaceInvariant(nullptr, MemberOffset(0), int_array_class);
- size_t component_size = int_array_class->GetComponentSize();
+ size_t component_size = int_array_class->GetComponentSize<kWithoutReadBarrier>();
CHECK_EQ(component_size, sizeof(int32_t));
size_t data_offset = mirror::Array::DataOffset(component_size).SizeValue();
if (data_offset > byte_size) {
@@ -1849,13 +1856,14 @@
} else {
// Use an int array.
dummy_obj->SetClass(int_array_class);
- CHECK(dummy_obj->IsArrayInstance());
+ CHECK((dummy_obj->IsArrayInstance<kVerifyNone, kWithoutReadBarrier>()));
int32_t length = (byte_size - data_offset) / component_size;
- dummy_obj->AsArray()->SetLength(length);
- CHECK_EQ(dummy_obj->AsArray()->GetLength(), length)
+ mirror::Array* dummy_arr = dummy_obj->AsArray<kVerifyNone, kWithoutReadBarrier>();
+ dummy_arr->SetLength(length);
+ CHECK_EQ(dummy_arr->GetLength(), length)
<< "byte_size=" << byte_size << " length=" << length
<< " component_size=" << component_size << " data_offset=" << data_offset;
- CHECK_EQ(byte_size, dummy_obj->SizeOf())
+ CHECK_EQ(byte_size, (dummy_obj->SizeOf<kVerifyNone, kWithoutReadBarrier>()))
<< "byte_size=" << byte_size << " length=" << length
<< " component_size=" << component_size << " data_offset=" << data_offset;
}
diff --git a/runtime/gc/reference_queue.cc b/runtime/gc/reference_queue.cc
index 6088a43..62625c4 100644
--- a/runtime/gc/reference_queue.cc
+++ b/runtime/gc/reference_queue.cc
@@ -44,7 +44,9 @@
// 1 element cyclic queue, ie: Reference ref = ..; ref.pendingNext = ref;
list_ = ref;
} else {
- mirror::Reference* head = list_->GetPendingNext();
+ // The list is owned by the GC, everything that has been inserted must already be at least
+ // gray.
+ mirror::Reference* head = list_->GetPendingNext<kWithoutReadBarrier>();
DCHECK(head != nullptr);
ref->SetPendingNext(head);
}
@@ -54,14 +56,14 @@
mirror::Reference* ReferenceQueue::DequeuePendingReference() {
DCHECK(!IsEmpty());
- mirror::Reference* ref = list_->GetPendingNext();
+ mirror::Reference* ref = list_->GetPendingNext<kWithoutReadBarrier>();
DCHECK(ref != nullptr);
// Note: the following code is thread-safe because it is only called from ProcessReferences which
// is single threaded.
if (list_ == ref) {
list_ = nullptr;
} else {
- mirror::Reference* next = ref->GetPendingNext();
+ mirror::Reference* next = ref->GetPendingNext<kWithoutReadBarrier>();
list_->SetPendingNext(next);
}
ref->SetPendingNext(nullptr);
diff --git a/runtime/mirror/class.h b/runtime/mirror/class.h
index 32ed337..3ba9e1a 100644
--- a/runtime/mirror/class.h
+++ b/runtime/mirror/class.h
@@ -471,7 +471,7 @@
template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
size_t GetComponentSize() SHARED_REQUIRES(Locks::mutator_lock_) {
- return 1U << GetComponentSizeShift();
+ return 1U << GetComponentSizeShift<kReadBarrierOption>();
}
template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
diff --git a/runtime/mirror/reference.h b/runtime/mirror/reference.h
index 3baa12e..e8ad5fa 100644
--- a/runtime/mirror/reference.h
+++ b/runtime/mirror/reference.h
@@ -76,8 +76,9 @@
SetFieldObjectVolatile<kTransactionActive>(ReferentOffset(), nullptr);
}
+ template <ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
Reference* GetPendingNext() SHARED_REQUIRES(Locks::mutator_lock_) {
- return GetFieldObject<Reference>(PendingNextOffset());
+ return GetFieldObject<Reference, kDefaultVerifyFlags, kReadBarrierOption>(PendingNextOffset());
}
void SetPendingNext(Reference* pending_next)
@@ -102,7 +103,7 @@
// removed from the list after having determined the reference is not ready
// to be enqueued on a java ReferenceQueue.
bool IsUnprocessed() SHARED_REQUIRES(Locks::mutator_lock_) {
- return GetPendingNext() == nullptr;
+ return GetPendingNext<kWithoutReadBarrier>() == nullptr;
}
template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
