commit 893263b7d5bc2ca43a91ecb8071867f5134fc60a
author Mathieu Chartier <mathieuc@google.com> Tue Mar 04 11:07:42 2014 -0800
committer Mathieu Chartier <mathieuc@google.com> Tue Mar 04 14:21:58 2014 -0800
tree a99238843a9caad00122c8f7d13e031f5d81bc38
parent 2fece5941f12395a94e742313e7059a9e419994d

Avoid marking old class linker and intern table roots during pause.

The new root visiting logic has a concept of a root log which holds
new roots which were added since the start of the GC. This is an
optimization since it lets us only mark these newly added roots
during the pause (or pre-cleaning) since the other roots intern table
and class linker roots were marked concurrently at the start of the
GC.

Before (EvaluateAndApplyChanges):
MarkConcurrentRoots:	Sum: 605.193ms
After:
MarkConcurrentRoots:	Sum: 271.858ms

This should also reduce pathological GC pauses which used to be able
to happen when the intern table or class linker became "dirty"
during the concurrent GC.

Change-Id: I433fab021f2c339d50c35aaae7161a50a0901dec

runtime/gc/collector/mark_sweep.h

diff --git a/runtime/gc/collector/mark_sweep.h b/runtime/gc/collector/mark_sweep.h
index c55b2b2..5c0a233 100644
--- a/runtime/gc/collector/mark_sweep.h
+++ b/runtime/gc/collector/mark_sweep.h
@@ -36,6 +36,7 @@
 
 class StackVisitor;
 class Thread;
+enum VisitRootFlags : uint8_t;
 
 namespace gc {
 
@@ -85,8 +86,8 @@
   // Find the default mark bitmap.
   void FindDefaultMarkBitmap();
 
-  // Marks the root set at the start of a garbage collection.
-  void MarkRoots()
+  // Marks all objects in the root set at the start of a garbage collection.
+  void MarkRoots(Thread* self)
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
@@ -94,7 +95,7 @@
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
-  void MarkConcurrentRoots()
+  void MarkConcurrentRoots(VisitRootFlags flags)
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
@@ -193,6 +194,11 @@
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
 
+  static void VerifyRootMarked(mirror::Object** root, void* arg, uint32_t /*thread_id*/,
+                               RootType /*root_type*/)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
+      EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
+
   static void ProcessMarkStackPausedCallback(void* arg)
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
 
@@ -205,10 +211,6 @@
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
 
-  void MarkRoot(const mirror::Object* obj)
-      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
-      EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
-
   Barrier& GetBarrier() {
     return *gc_barrier_;
   }