Check for forwarding address in READ_BARRIER_MARK_REG
When the object is in the from-space, the mark bit is not set.
In this case, we can also check the lock word for being a forwarding
address. The forwarding address case happens around 25% of the time.
This CL adds the case for forwarding address lock words to
READ_BARRIER_MARK_REG.
Reduces total read barriers reaching runtime on ritzperf:
Slow paths: 20758783 -> 15457783
Deleted the mark bit check in MarkFromReadBarrier since most of the
callers check the bit now.
Perf:
ReadBarrier::Mark: 2.59% -> 2.12%
art_quick_read_barrier_mark_reg01: 0.79% -> 0.78%
art_quick_read_barrier_mark_reg00: 0.54% -> 0.50%
art_quick_read_barrier_mark_reg02: 0.31% -> 0.25%
Only X86_64 for now, will do other archs after.
Bug: 30162165
Test: test-art-host
Change-Id: Ie7289d684d0e37a887943d77710092e380457860
diff --git a/runtime/gc/collector/concurrent_copying-inl.h b/runtime/gc/collector/concurrent_copying-inl.h
index 76f500c..b23897b 100644
--- a/runtime/gc/collector/concurrent_copying-inl.h
+++ b/runtime/gc/collector/concurrent_copying-inl.h
@@ -155,7 +155,7 @@
mirror::Object* ret;
// TODO: Delete GetMarkBit check when all of the callers properly check the bit. Remaining caller
// is array allocations.
- if (from_ref == nullptr || from_ref->GetMarkBit()) {
+ if (from_ref == nullptr) {
return from_ref;
}
// TODO: Consider removing this check when we are done investigating slow paths. b/30162165