Reverts CLs related to the TLAB due to heap exhaustion.

runtime/vm/scavenger.cc

Index: runtime/vm/scavenger.cc
diff --git a/runtime/vm/scavenger.cc b/runtime/vm/scavenger.cc
index 3118417cc839e65e219e7946c092a1f820e3c378..6e34bd0fa65fabbc9fa9afaffb19fbf255f12812 100644
--- a/runtime/vm/scavenger.cc
+++ b/runtime/vm/scavenger.cc
@@ -394,6 +394,13 @@ SemiSpace* Scavenger::Prologue(Isolate* isolate, bool invoke_api_callbacks) {
   resolved_top_ = top_;
   end_ = to_->end();
 
+  // Throw out the old information about the from space
+  if (isolate->IsMutatorThreadScheduled()) {
+    Thread* mutator_thread = isolate->mutator_thread();
+    mutator_thread->set_top(top_);
+    mutator_thread->set_end(end_);
+  }
+
   return from;
 }
 
@@ -403,10 +410,13 @@ void Scavenger::Epilogue(Isolate* isolate,
   // All objects in the to space have been copied from the from space at this
   // moment.
 
-  // Ensure the mutator thread will fail the next allocation. This will force
-  // mutator to allocate a new TLAB
-  Thread* mutator_thread = isolate->mutator_thread();
-  ASSERT((mutator_thread == NULL) || (!mutator_thread->HasActiveTLAB()));
+  // Ensure the mutator thread now has the up-to-date top_ and end_ of the
+  // semispace
+  if (isolate->IsMutatorThreadScheduled()) {
+    Thread* thread = isolate->mutator_thread();
+    thread->set_top(top_);
+    thread->set_end(end_);
+  }
 
   double avg_frac = stats_history_.Get(0).PromoCandidatesSuccessFraction();
   if (stats_history_.Size() >= 2) {
@@ -712,22 +722,18 @@ void Scavenger::ProcessWeakReferences() {
   }
 }
 
-void Scavenger::MakeNewSpaceIterable() const {
+void Scavenger::FlushTLS() const {
   ASSERT(heap_ != NULL);
-  Thread* mutator_thread = heap_->isolate()->mutator_thread();
-  if (mutator_thread != NULL && !scavenging_) {
-    if (mutator_thread->HasActiveTLAB()) {
-      ASSERT(mutator_thread->top() <=
-             mutator_thread->heap()->new_space()->top());
-      heap_->FillRemainingTLAB(mutator_thread);
-    }
+  if (heap_->isolate()->IsMutatorThreadScheduled()) {
+    Thread* mutator_thread = heap_->isolate()->mutator_thread();
+    mutator_thread->heap()->new_space()->set_top(mutator_thread->top());
   }
 }
 
 void Scavenger::VisitObjectPointers(ObjectPointerVisitor* visitor) const {
   ASSERT(Thread::Current()->IsAtSafepoint() ||
          (Thread::Current()->task_kind() == Thread::kMarkerTask));
-  MakeNewSpaceIterable();
+  FlushTLS();
   uword cur = FirstObjectStart();
   while (cur < top_) {
     RawObject* raw_obj = RawObject::FromAddr(cur);
@@ -738,7 +744,7 @@ void Scavenger::VisitObjectPointers(ObjectPointerVisitor* visitor) const {
 void Scavenger::VisitObjects(ObjectVisitor* visitor) const {
   ASSERT(Thread::Current()->IsAtSafepoint() ||
          (Thread::Current()->task_kind() == Thread::kMarkerTask));
-  MakeNewSpaceIterable();
+  FlushTLS();
   uword cur = FirstObjectStart();
   while (cur < top_) {
     RawObject* raw_obj = RawObject::FromAddr(cur);
@@ -753,7 +759,7 @@ void Scavenger::AddRegionsToObjectSet(ObjectSet* set) const {
 
 RawObject* Scavenger::FindObject(FindObjectVisitor* visitor) const {
   ASSERT(!scavenging_);
-  MakeNewSpaceIterable();
+  FlushTLS();
   uword cur = FirstObjectStart();
   if (visitor->VisitRange(cur, top_)) {
     while (cur < top_) {
@@ -800,11 +806,6 @@ void Scavenger::Scavenge(bool invoke_api_callbacks) {
   int64_t post_safe_point = OS::GetCurrentMonotonicMicros();
   heap_->RecordTime(kSafePoint, post_safe_point - pre_safe_point);
 
-  Thread* mutator_thread = isolate->mutator_thread();
-  if ((mutator_thread != NULL) && (mutator_thread->HasActiveTLAB())) {
-    heap_->AbandonRemainingTLAB(mutator_thread);
-  }
-
   // TODO(koda): Make verification more compatible with concurrent sweep.
   if (FLAG_verify_before_gc && !FLAG_concurrent_sweep) {
     OS::PrintErr("Verifying before Scavenge...");
@@ -916,6 +917,11 @@ void Scavenger::Evacuate() {
   // Forces the next scavenge to promote all the objects in the new space.
   survivor_end_ = top_;
 
+  if (heap_->isolate()->IsMutatorThreadScheduled()) {
+    Thread* mutator_thread = heap_->isolate()->mutator_thread();
+    survivor_end_ = mutator_thread->top();
+  }
+
   Scavenge();
 
   // It is possible for objects to stay in the new space
@@ -923,17 +929,4 @@ void Scavenger::Evacuate() {
   ASSERT((UsedInWords() == 0) || failed_to_promote_);
 }
 
-int64_t Scavenger::UsedInWords() const {
-  int64_t free_space_in_tlab = 0;
-  if (heap_->isolate()->IsMutatorThreadScheduled()) {
-    Thread* mutator_thread = heap_->isolate()->mutator_thread();
-    if (mutator_thread->HasActiveTLAB()) {
-      free_space_in_tlab =
-          (mutator_thread->end() - mutator_thread->top()) >> kWordSizeLog2;
-    }
-  }
-  int64_t max_space_used = (top_ - FirstObjectStart()) >> kWordSizeLog2;
-  return max_space_used - free_space_in_tlab;
-}
-
 }  // namespace dart