commit a1c1c71e24c93a720bbf13de129c75a9a0bde37a
author Mathieu Chartier <mathieuc@google.com> Mon Jun 23 17:53:09 2014 -0700
committer Mathieu Chartier <mathieuc@google.com> Mon Jun 23 17:55:22 2014 -0700
tree 7c86b8684123587894997077680fdc7324954f9c
parent 9462a31caedefac3e04bd4aa5088e050ed188b30

Use reader lock of bulk free lock when not freeing.

Should help reduce contention observed in systrace.

Change-Id: Iadb81728d4ba797c3a68acea795b15d7f212e89b

runtime/gc/allocator/rosalloc.cc

diff --git a/runtime/gc/allocator/rosalloc.cc b/runtime/gc/allocator/rosalloc.cc
index 55262f2..656c55b 100644
--- a/runtime/gc/allocator/rosalloc.cc
+++ b/runtime/gc/allocator/rosalloc.cc
@@ -529,7 +529,7 @@
 }
 
 size_t RosAlloc::Free(Thread* self, void* ptr) {
-  ReaderMutexLock rmu(self, bulk_free_lock_);
+  WriterMutexLock rmu(self, bulk_free_lock_);
   return FreeInternal(self, ptr);
 }
 
@@ -1642,7 +1642,7 @@
 void RosAlloc::RevokeThreadLocalRuns(Thread* thread) {
   Thread* self = Thread::Current();
   // Avoid race conditions on the bulk free bit maps with BulkFree() (GC).
-  WriterMutexLock wmu(self, bulk_free_lock_);
+  ReaderMutexLock wmu(self, bulk_free_lock_);
   for (size_t idx = 0; idx < kNumThreadLocalSizeBrackets; idx++) {
     MutexLock mu(self, *size_bracket_locks_[idx]);
     Run* thread_local_run = reinterpret_cast<Run*>(thread->GetRosAllocRun(idx));
@@ -1720,7 +1720,7 @@
   if (kIsDebugBuild) {
     Thread* self = Thread::Current();
     // Avoid race conditions on the bulk free bit maps with BulkFree() (GC).
-    WriterMutexLock wmu(self, bulk_free_lock_);
+    ReaderMutexLock wmu(self, bulk_free_lock_);
     for (size_t idx = 0; idx < kNumThreadLocalSizeBrackets; idx++) {
       MutexLock mu(self, *size_bracket_locks_[idx]);
       Run* thread_local_run = reinterpret_cast<Run*>(thread->GetRosAllocRun(idx));
@@ -1867,7 +1867,7 @@
   CHECK(Locks::mutator_lock_->IsExclusiveHeld(self))
       << "The mutator locks isn't exclusively locked at RosAlloc::Verify()";
   MutexLock mu(self, *Locks::thread_list_lock_);
-  WriterMutexLock wmu(self, bulk_free_lock_);
+  ReaderMutexLock wmu(self, bulk_free_lock_);
   std::vector<Run*> runs;
   {
     MutexLock mu(self, lock_);

runtime/gc/allocator/rosalloc.h

diff --git a/runtime/gc/allocator/rosalloc.h b/runtime/gc/allocator/rosalloc.h
index a439188..13f61ec 100644
--- a/runtime/gc/allocator/rosalloc.h
+++ b/runtime/gc/allocator/rosalloc.h
@@ -45,10 +45,7 @@
     byte magic_num_;  // The magic number used for debugging only.
 
     bool IsFree() const {
-      if (kIsDebugBuild) {
-        return magic_num_ == kMagicNumFree;
-      }
-      return true;
+      return !kIsDebugBuild || magic_num_ == kMagicNumFree;
     }
     size_t ByteSize(RosAlloc* rosalloc) const EXCLUSIVE_LOCKS_REQUIRED(rosalloc->lock_) {
       const byte* fpr_base = reinterpret_cast<const byte*>(this);