Change one read barrier bit to mark bit
Optimization to help slow path performance. When the GC marks an
object through the read barrier slow path. The GC sets the mark bit
in the lock word of that reference. This bit is checked from the
assembly entrypoint the common case is that it is set. If the bit is
set, the read barrier knows the object is already marked and there is
no work to do.
To prevent dirty pages in zygote and image, the bit is set by the
image writer and zygote space creation.
EAAC score (lower is better):
N9: 777 -> 700 (average 31 of runs)
N6P (960000 mhz): 1737.48 -> 1442.31 (average of 25 runs)
Bug: 30162165
Bug: 12687968
Test: N9, N6P booting, test-art-host, test-art-target all with CC
Change-Id: Iae0cacfae221e33151d3c0ab65338d1c822ab63d
diff --git a/runtime/monitor.cc b/runtime/monitor.cc
index bf9f931..e863ea9 100644
--- a/runtime/monitor.cc
+++ b/runtime/monitor.cc
@@ -155,7 +155,7 @@
return false;
}
}
- LockWord fat(this, lw.ReadBarrierState());
+ LockWord fat(this, lw.GCState());
// Publish the updated lock word, which may race with other threads.
bool success = GetObject()->CasLockWordWeakSequentiallyConsistent(lw, fat);
// Lock profiling.
@@ -774,20 +774,21 @@
return false;
}
// Deflate to a thin lock.
- LockWord new_lw = LockWord::FromThinLockId(owner->GetThreadId(), monitor->lock_count_,
- lw.ReadBarrierState());
+ LockWord new_lw = LockWord::FromThinLockId(owner->GetThreadId(),
+ monitor->lock_count_,
+ lw.GCState());
// Assume no concurrent read barrier state changes as mutators are suspended.
obj->SetLockWord(new_lw, false);
VLOG(monitor) << "Deflated " << obj << " to thin lock " << owner->GetTid() << " / "
<< monitor->lock_count_;
} else if (monitor->HasHashCode()) {
- LockWord new_lw = LockWord::FromHashCode(monitor->GetHashCode(), lw.ReadBarrierState());
+ LockWord new_lw = LockWord::FromHashCode(monitor->GetHashCode(), lw.GCState());
// Assume no concurrent read barrier state changes as mutators are suspended.
obj->SetLockWord(new_lw, false);
VLOG(monitor) << "Deflated " << obj << " to hash monitor " << monitor->GetHashCode();
} else {
// No lock and no hash, just put an empty lock word inside the object.
- LockWord new_lw = LockWord::FromDefault(lw.ReadBarrierState());
+ LockWord new_lw = LockWord::FromDefault(lw.GCState());
// Assume no concurrent read barrier state changes as mutators are suspended.
obj->SetLockWord(new_lw, false);
VLOG(monitor) << "Deflated" << obj << " to empty lock word";
@@ -876,7 +877,7 @@
LockWord lock_word = h_obj->GetLockWord(true);
switch (lock_word.GetState()) {
case LockWord::kUnlocked: {
- LockWord thin_locked(LockWord::FromThinLockId(thread_id, 0, lock_word.ReadBarrierState()));
+ LockWord thin_locked(LockWord::FromThinLockId(thread_id, 0, lock_word.GCState()));
if (h_obj->CasLockWordWeakSequentiallyConsistent(lock_word, thin_locked)) {
AtraceMonitorLock(self, h_obj.Get(), false /* is_wait */);
// CasLockWord enforces more than the acquire ordering we need here.
@@ -890,8 +891,9 @@
// We own the lock, increase the recursion count.
uint32_t new_count = lock_word.ThinLockCount() + 1;
if (LIKELY(new_count <= LockWord::kThinLockMaxCount)) {
- LockWord thin_locked(LockWord::FromThinLockId(thread_id, new_count,
- lock_word.ReadBarrierState()));
+ LockWord thin_locked(LockWord::FromThinLockId(thread_id,
+ new_count,
+ lock_word.GCState()));
if (!kUseReadBarrier) {
h_obj->SetLockWord(thin_locked, true);
AtraceMonitorLock(self, h_obj.Get(), false /* is_wait */);
@@ -975,9 +977,9 @@
LockWord new_lw = LockWord::Default();
if (lock_word.ThinLockCount() != 0) {
uint32_t new_count = lock_word.ThinLockCount() - 1;
- new_lw = LockWord::FromThinLockId(thread_id, new_count, lock_word.ReadBarrierState());
+ new_lw = LockWord::FromThinLockId(thread_id, new_count, lock_word.GCState());
} else {
- new_lw = LockWord::FromDefault(lock_word.ReadBarrierState());
+ new_lw = LockWord::FromDefault(lock_word.GCState());
}
if (!kUseReadBarrier) {
DCHECK_EQ(new_lw.ReadBarrierState(), 0U);