Scan immune spaces using mod union tables.

It's faster to scan the immune spaces using the mod union tables (gray
objects on dirty pages) than the live bitmaps (gray objects).

The immune space scan time goes from ~13ms down to ~10ms in the
testWidgetsContainerFling test on angler at 1 GHz.

Change-Id: I0914d7bdb50cbf8a49c859070a3501b48eb79f3e
Test: N9 boot, art tests, Ritz EAAC.
Bug: 29516968
Bug: 29517059
Bug: 12687968

diff --git a/runtime/gc/collector/concurrent_copying.cc b/runtime/gc/collector/concurrent_copying.cc
index d413a50..4a80089 100644 (file)
--- a/runtime/gc/collector/concurrent_copying.cc
+++ b/runtime/gc/collector/concurrent_copying.cc
@@ -520,7 +520,7 @@ class ConcurrentCopying::ImmuneSpaceScanObjVisitor {
   explicit ImmuneSpaceScanObjVisitor(ConcurrentCopying* cc)
       : collector_(cc) {}
 
-  void operator()(mirror::Object* obj) const SHARED_REQUIRES(Locks::mutator_lock_) {
+  ALWAYS_INLINE void operator()(mirror::Object* obj) const SHARED_REQUIRES(Locks::mutator_lock_) {
     if (kUseBakerReadBarrier && kGrayDirtyImmuneObjects) {
       if (obj->GetReadBarrierPointer() == ReadBarrier::GrayPtr()) {
         collector_->ScanImmuneObject(obj);
@@ -534,6 +534,10 @@ class ConcurrentCopying::ImmuneSpaceScanObjVisitor {
     }
   }
 
+  static void Callback(mirror::Object* obj, void* arg) SHARED_REQUIRES(Locks::mutator_lock_) {
+    reinterpret_cast<ImmuneSpaceScanObjVisitor*>(arg)->operator()(obj);
+  }
+
  private:
   ConcurrentCopying* const collector_;
 };
@@ -558,10 +562,15 @@ void ConcurrentCopying::MarkingPhase() {
     for (auto& space : immune_spaces_.GetSpaces()) {
       DCHECK(space->IsImageSpace() || space->IsZygoteSpace());
       accounting::ContinuousSpaceBitmap* live_bitmap = space->GetLiveBitmap();
+      accounting::ModUnionTable* table = heap_->FindModUnionTableFromSpace(space);
       ImmuneSpaceScanObjVisitor visitor(this);
-      live_bitmap->VisitMarkedRange(reinterpret_cast<uintptr_t>(space->Begin()),
-                                    reinterpret_cast<uintptr_t>(space->Limit()),
-                                    visitor);
+      if (table != nullptr) {
+        table->VisitObjects(ImmuneSpaceScanObjVisitor::Callback, &visitor);
+      } else {
+        live_bitmap->VisitMarkedRange(reinterpret_cast<uintptr_t>(space->Begin()),
+                                      reinterpret_cast<uintptr_t>(space->Limit()),
+                                      visitor);
+      }
     }
   }
   if (kUseBakerReadBarrier) {