Moves the top_ and end_ words of the Scavenger into mutator thread.

runtime/vm/scavenger.cc

Index: runtime/vm/scavenger.cc
diff --git a/runtime/vm/scavenger.cc b/runtime/vm/scavenger.cc
index a13bcce75a27f8ceee815933cd333ac69f8ebe6e..1e319bf66c416d367bfde9d26547664acb0f4404 100644
--- a/runtime/vm/scavenger.cc
+++ b/runtime/vm/scavenger.cc
@@ -338,7 +338,8 @@ Scavenger::Scavenger(Heap* heap,
       delayed_weak_properties_(NULL),
       gc_time_micros_(0),
       collections_(0),
-      external_size_(0) {
+      external_size_(0),
+      space_lock_(new Mutex()) {
   // Verify assumptions about the first word in objects which the scavenger is
   // going to use for forwarding pointers.
   ASSERT(Object::tags_offset() == 0);
@@ -370,6 +371,7 @@ Scavenger::Scavenger(Heap* heap,
 Scavenger::~Scavenger() {
   ASSERT(!scavenging_);
   to_->Delete();
+  delete space_lock_;
 }
 
 
@@ -392,6 +394,12 @@ SemiSpace* Scavenger::Prologue(Isolate* isolate, bool invoke_api_callbacks) {
     (isolate->gc_prologue_callback())();
   }
   isolate->PrepareForGC();
+
+  Thread* thread = Thread::Current();

[rmacnak, 2017/07/05 17:39:53]

How about

Thread* mutator = isolate->mutator_thread()

?

[danunez, 2017/07/05 18:12:55]

Done.

+  if (!thread->IsMutatorThread()) {
+    thread = isolate->mutator_thread();
+  }
+
   // Flip the two semi-spaces so that to_ is always the space for allocating
   // objects.
   SemiSpace* from = to_;
@@ -409,6 +417,12 @@ SemiSpace* Scavenger::Prologue(Isolate* isolate, bool invoke_api_callbacks) {
   top_ = FirstObjectStart();
   resolved_top_ = top_;
   end_ = to_->end();
+
+  if (thread->heap() != NULL) {
+    thread->set_top_offset(top_);
+    thread->set_end_offset(end_);
+  }
+
   return from;
 }
 
@@ -418,6 +432,25 @@ void Scavenger::Epilogue(Isolate* isolate,
                          bool invoke_api_callbacks) {
   // All objects in the to space have been copied from the from space at this
   // moment.
+
+  Thread* thread = Thread::Current();
+
+  if (!thread->IsMutatorThread()) {
+    thread = isolate->mutator_thread();
+  }
+  uword top = 0;
+  uword end = 0;
+
+
+  if (thread->heap() != NULL) {
+    top = thread->top();
+    ASSERT(thread->end() == end_);
+    end = thread->end();
+  } else {
+    top = top_;
+    end = end_;
+  }
+
   double avg_frac = stats_history_.Get(0).PromoCandidatesSuccessFraction();
   if (stats_history_.Size() >= 2) {
     // Previous scavenge is only given half as much weight.
@@ -426,11 +459,11 @@ void Scavenger::Epilogue(Isolate* isolate,
   }
   if (avg_frac < (FLAG_early_tenuring_threshold / 100.0)) {
     // Remember the limit to which objects have been copied.
-    survivor_end_ = top_;
+    survivor_end_ = top;
   } else {
     // Move survivor end to the end of the to_ space, making all surviving
     // objects candidates for promotion next time.
-    survivor_end_ = end_;
+    survivor_end_ = end;
   }
 #if defined(DEBUG)
   // We can only safely verify the store buffers from old space if there is no
@@ -554,8 +587,22 @@ void Scavenger::IterateWeakRoots(Isolate* isolate, HandleVisitor* visitor) {
 
 void Scavenger::ProcessToSpace(ScavengerVisitor* visitor) {
   // Iterate until all work has been drained.
-  while ((resolved_top_ < top_) || PromotedStackHasMore()) {
-    while (resolved_top_ < top_) {
+
+  uword top = 0;
+  Thread* thread = Thread::Current();
+
+  if (!thread->IsMutatorThread()) {
+    thread = Isolate::Current()->mutator_thread();
+  }
+
+  if (thread->heap() != NULL) {
+    top = thread->top();
+  } else {
+    top = top_;
+  }
+
+  while ((resolved_top_ < top) || PromotedStackHasMore()) {
+    while (resolved_top_ < top) {
       RawObject* raw_obj = RawObject::FromAddr(resolved_top_);
       intptr_t class_id = raw_obj->GetClassId();
       if (class_id != kWeakPropertyCid) {
@@ -564,6 +611,12 @@ void Scavenger::ProcessToSpace(ScavengerVisitor* visitor) {
         RawWeakProperty* raw_weak = reinterpret_cast<RawWeakProperty*>(raw_obj);
         resolved_top_ += ProcessWeakProperty(raw_weak, visitor);
       }
+
+      if (thread->heap() != NULL) {
+        top = thread->top();
+      } else {
+        top = top_;
+      }
     }
     {
       // Visit all the promoted objects and update/scavenge their internal
@@ -576,6 +629,12 @@ void Scavenger::ProcessToSpace(ScavengerVisitor* visitor) {
         ASSERT(!raw_object->IsRemembered());
         visitor->VisitingOldObject(raw_object);
         raw_object->VisitPointersNonvirtual(visitor);
+
+        if (thread->heap() != NULL) {
+          top = thread->top();
+        } else {
+          top = top_;
+        }
       }
       visitor->VisitingOldObject(NULL);
     }
@@ -606,6 +665,13 @@ void Scavenger::ProcessToSpace(ScavengerVisitor* visitor) {
         } else {
           EnqueueWeakProperty(cur_weak);
         }
+
+        if (thread->heap() != NULL) {
+          top = thread->top();
+        } else {
+          top = top_;
+        }
+
         // Advance to next weak property in the queue.
         cur_weak = reinterpret_cast<RawWeakProperty*>(next_weak);
       }
@@ -732,7 +798,19 @@ void Scavenger::ProcessWeakReferences() {
 
 void Scavenger::VisitObjectPointers(ObjectPointerVisitor* visitor) const {
   uword cur = FirstObjectStart();
-  while (cur < top_) {
+  Thread* thread = Thread::Current();
+
+  if (!thread->IsMutatorThread()) {

[rmacnak, 2017/07/05 17:39:53]

Ditto

[danunez, 2017/07/05 18:12:55]

Done.

+    thread = Isolate::Current()->mutator_thread();
+  }
+
+  uword top = CapacityInWords() == 0 ? 0 : thread->top();
+
+  if (thread->heap() == NULL) {
+    top = top_;
+  }
+
+  while (cur < top) {
     RawObject* raw_obj = RawObject::FromAddr(cur);
     cur += raw_obj->VisitPointers(visitor);
   }
@@ -741,7 +819,19 @@ void Scavenger::VisitObjectPointers(ObjectPointerVisitor* visitor) const {
 
 void Scavenger::VisitObjects(ObjectVisitor* visitor) const {
   uword cur = FirstObjectStart();
-  while (cur < top_) {
+  Thread* thread = Thread::Current();
+
+  if (!thread->IsMutatorThread()) {

[rmacnak, 2017/07/05 17:39:53]

Ditto

[danunez, 2017/07/05 18:12:55]

Done.

+    thread = Isolate::Current()->mutator_thread();
+  }
+
+  uword top = CapacityInWords() == 0 ? 0 : thread->top();
+
+  if (thread->heap() == NULL) {
+    top = top_;
+  }
+
+  while (cur < top) {
     RawObject* raw_obj = RawObject::FromAddr(cur);
     visitor->VisitObject(raw_obj);
     cur += raw_obj->Size();
@@ -756,9 +846,21 @@ void Scavenger::AddRegionsToObjectSet(ObjectSet* set) const {
 
 RawObject* Scavenger::FindObject(FindObjectVisitor* visitor) const {
   ASSERT(!scavenging_);
+  Thread* thread = Thread::Current();
+
+  if (!thread->IsMutatorThread()) {

[rmacnak, 2017/07/05 17:39:52]

Ditto

[danunez, 2017/07/05 18:12:55]

Done.

+    thread = Isolate::Current()->mutator_thread();
+  }
+
+  uword top = CapacityInWords() == 0 ? 0 : thread->top();
   uword cur = FirstObjectStart();
-  if (visitor->VisitRange(cur, top_)) {
-    while (cur < top_) {
+
+  if (thread->heap() == NULL) {
+    top = top_;
+  }
+
+  if (visitor->VisitRange(cur, top)) {
+    while (cur < top) {
       RawObject* raw_obj = RawObject::FromAddr(cur);
       uword next = cur + raw_obj->Size();
       if (visitor->VisitRange(cur, next) && raw_obj->FindObject(visitor)) {
@@ -766,7 +868,6 @@ RawObject* Scavenger::FindObject(FindObjectVisitor* visitor) const {
       }
       cur = next;
     }
-    ASSERT(cur == top_);
   }
   return Object::null();
 }