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

runtime/vm/scavenger.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/scavenger.h"
 
 #include "vm/dart.h"
 #include "vm/dart_api_state.h"
 #include "vm/isolate.h"
 #include "vm/lockers.h"
@@ skipping 319 matching lines @@
 Scavenger::Scavenger(Heap* heap,
                      intptr_t max_semi_capacity_in_words,
                      uword object_alignment)
     : heap_(heap),
       max_semi_capacity_in_words_(max_semi_capacity_in_words),
       object_alignment_(object_alignment),
       scavenging_(false),
       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);
 
   // Set initial size resulting in a total of three different levels.
   const intptr_t initial_semi_capacity_in_words =
       max_semi_capacity_in_words /
       (FLAG_new_gen_growth_factor * FLAG_new_gen_growth_factor);
   to_ = SemiSpace::New(initial_semi_capacity_in_words);
   if (to_ == NULL) {
     OUT_OF_MEMORY();
   }
   // Setup local fields.
   top_ = FirstObjectStart();
   resolved_top_ = top_;
   end_ = to_->end();
 
   survivor_end_ = FirstObjectStart();
 
   UpdateMaxHeapCapacity();
   UpdateMaxHeapUsage();
 }
 
 
 Scavenger::~Scavenger() {
   ASSERT(!scavenging_);
   to_->Delete();
+  delete space_lock_;
 }
 
 
 intptr_t Scavenger::NewSizeInWords(intptr_t old_size_in_words) const {
   if (stats_history_.Size() == 0) {
     return old_size_in_words;
   }
   double garbage = stats_history_.Get(0).GarbageFraction();
   if (garbage < (FLAG_new_gen_garbage_threshold / 100.0)) {
     return Utils::Minimum(max_semi_capacity_in_words_,
                           old_size_in_words * FLAG_new_gen_growth_factor);
   } else {
     return old_size_in_words;
   }
 }
 
 
 SemiSpace* Scavenger::Prologue(Isolate* isolate, bool invoke_api_callbacks) {
   if (invoke_api_callbacks && (isolate->gc_prologue_callback() != NULL)) {
     (isolate->gc_prologue_callback())();
   }
   isolate->PrepareForGC();
+
+  ASSERT(isolate->mutator_thread()->top() == top_);
+
   // Flip the two semi-spaces so that to_ is always the space for allocating
   // objects.
   SemiSpace* from = to_;
   to_ = SemiSpace::New(NewSizeInWords(from->size_in_words()));
   if (to_ == NULL) {
     // TODO(koda): We could try to recover (collect old space, wait for another
     // isolate to finish scavenge, etc.).
     OUT_OF_MEMORY();
   }
   UpdateMaxHeapCapacity();
   top_ = FirstObjectStart();
   resolved_top_ = top_;
   end_ = to_->end();
+
+  isolate->mutator_thread()->set_top_offset(top_);
+  isolate->mutator_thread()->set_end_offset(end_);
+
   return from;
 }
 
 
 void Scavenger::Epilogue(Isolate* isolate,
                          SemiSpace* from,
                          bool invoke_api_callbacks) {
   // All objects in the to space have been copied from the from space at this
   // moment.
+
+  isolate->mutator_thread()->set_top_offset(top_);
+  isolate->mutator_thread()->set_end_offset(end_);
+
   double avg_frac = stats_history_.Get(0).PromoCandidatesSuccessFraction();
   if (stats_history_.Size() >= 2) {
     // Previous scavenge is only given half as much weight.
     avg_frac += 0.5 * stats_history_.Get(1).PromoCandidatesSuccessFraction();
     avg_frac /= 1.0 + 0.5;  // Normalize.
   }
   if (avg_frac < (FLAG_early_tenuring_threshold / 100.0)) {
     // Remember the limit to which objects have been copied.
     survivor_end_ = top_;
   } else {
@@ skipping 116 matching lines @@
 }
 
 
 void Scavenger::IterateWeakRoots(Isolate* isolate, HandleVisitor* visitor) {
   isolate->VisitWeakPersistentHandles(visitor);
 }
 
 
 void Scavenger::ProcessToSpace(ScavengerVisitor* visitor) {
   // Iterate until all work has been drained.
+
+  ASSERT(Isolate::Current()->mutator_thread()->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) {
         resolved_top_ += raw_obj->VisitPointersNonvirtual(visitor);
       } else {
         RawWeakProperty* raw_weak = reinterpret_cast<RawWeakProperty*>(raw_obj);
         resolved_top_ += ProcessWeakProperty(raw_weak, visitor);
       }
@@ skipping 158 matching lines @@
 
       // Advance to next weak property in the queue.
       cur_weak = reinterpret_cast<RawWeakProperty*>(next_weak);
     }
   }
 }
 
 
 void Scavenger::VisitObjectPointers(ObjectPointerVisitor* visitor) const {
   uword cur = FirstObjectStart();
   while (cur < top_) {

[rmacnak, 2017/06/22 22:31:50]

top_ may be stale

[danunez, 2017/06/30 20:35:57]

Right. top_ is now retrieved from the mutator thread if it is still scheduled.

     RawObject* raw_obj = RawObject::FromAddr(cur);
     cur += raw_obj->VisitPointers(visitor);
   }
 }
 
 
 void Scavenger::VisitObjects(ObjectVisitor* visitor) const {
   uword cur = FirstObjectStart();
   while (cur < top_) {

[rmacnak, 2017/06/22 22:31:50]

top_ may be stale

[danunez, 2017/06/30 20:35:57]

Right. top_ is now retrieved from the mutator thread if it is still scheduled.

     RawObject* raw_obj = RawObject::FromAddr(cur);
     visitor->VisitObject(raw_obj);
     cur += raw_obj->Size();
   }
 }
 
 
 void Scavenger::AddRegionsToObjectSet(ObjectSet* set) const {
   set->AddRegion(to_->start(), to_->end());
 }
 
 
 RawObject* Scavenger::FindObject(FindObjectVisitor* visitor) const {
   ASSERT(!scavenging_);
   uword cur = FirstObjectStart();
   if (visitor->VisitRange(cur, top_)) {

[rmacnak, 2017/06/22 22:31:50]

top_ may be stale

[danunez, 2017/06/30 20:35:57]

Right. top_ is now retrieved from the mutator thread if it is still scheduled.

     while (cur < top_) {
       RawObject* raw_obj = RawObject::FromAddr(cur);
       uword next = cur + raw_obj->Size();
       if (visitor->VisitRange(cur, next) && raw_obj->FindObject(visitor)) {
         return raw_obj;  // Found object, return it.
       }
       cur = next;
     }
     ASSERT(cur == top_);
   }
@@ skipping 128 matching lines @@
 }
 
 
 void Scavenger::FreeExternal(intptr_t size) {
   ASSERT(size >= 0);
   external_size_ -= size;
   ASSERT(external_size_ >= 0);
 }
 
 }  // namespace dart