[heap] Improve size profiling for ArrayBuffer tracking

src/heap/array-buffer-tracker.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/array-buffer-tracker.h"
 #include "src/heap/array-buffer-tracker-inl.h"
 #include "src/heap/heap.h"
 
 namespace v8 {
 namespace internal {
 
 LocalArrayBufferTracker::~LocalArrayBufferTracker() {
   CHECK(array_buffers_.empty());
 }
 
 template <LocalArrayBufferTracker::FreeMode free_mode>
-void LocalArrayBufferTracker::Free() {
+LocalArrayBufferTracker::ProcessResult LocalArrayBufferTracker::Free() {
   size_t freed_memory = 0;
+  size_t live_memory = 0;
   for (TrackingData::iterator it = array_buffers_.begin();
        it != array_buffers_.end();) {
     JSArrayBuffer* buffer = reinterpret_cast<JSArrayBuffer*>(it->first);
     if ((free_mode == kFreeAll) ||
         Marking::IsWhite(ObjectMarking::MarkBitFrom(buffer))) {
       const size_t len = it->second;
       heap_->isolate()->array_buffer_allocator()->Free(buffer->backing_store(),
                                                        len);
       freed_memory += len;
       it = array_buffers_.erase(it);
     } else {
+      live_memory += it->second;
       ++it;
     }
   }
-  if (freed_memory > 0) {
-    heap_->update_external_memory_concurrently_freed(
-        static_cast<intptr_t>(freed_memory));
-  }
+  return ProcessResult(freed_memory, live_memory, 0);
 }
 
 template <typename Callback>
-void LocalArrayBufferTracker::Process(Callback callback) {
+LocalArrayBufferTracker::ProcessResult LocalArrayBufferTracker::Process(
+    Callback callback) {
   JSArrayBuffer* new_buffer = nullptr;
   size_t freed_memory = 0;
+  size_t live_memory = 0;
+  size_t promoted_memory = 0;
   for (TrackingData::iterator it = array_buffers_.begin();
        it != array_buffers_.end();) {
     const CallbackResult result = callback(it->first, &new_buffer);
     if (result == kKeepEntry) {
+      live_memory += it->second;
       ++it;
     } else if (result == kUpdateEntry) {
       DCHECK_NOT_NULL(new_buffer);
       Page* target_page = Page::FromAddress(new_buffer->address());
       // We need to lock the target page because we cannot guarantee
       // exclusive access to new space pages.
       if (target_page->InNewSpace()) target_page->mutex()->Lock();
       LocalArrayBufferTracker* tracker = target_page->local_tracker();
       if (tracker == nullptr) {
         target_page->AllocateLocalTracker();
         tracker = target_page->local_tracker();
       }
       DCHECK_NOT_NULL(tracker);
       tracker->Add(new_buffer, it->second);
-      if (target_page->InNewSpace()) target_page->mutex()->Unlock();
+      if (target_page->InNewSpace()) {
+        target_page->mutex()->Unlock();
+        live_memory += it->second;
+      } else {
+        promoted_memory += it->second;
+      }
       it = array_buffers_.erase(it);
     } else if (result == kRemoveEntry) {
       const size_t len = it->second;
       heap_->isolate()->array_buffer_allocator()->Free(
           it->first->backing_store(), len);
       freed_memory += len;
       it = array_buffers_.erase(it);
     } else {
       UNREACHABLE();
     }
   }
-  if (freed_memory > 0) {
-    heap_->update_external_memory_concurrently_freed(
-        static_cast<intptr_t>(freed_memory));
-  }
+  return ProcessResult(freed_memory, live_memory, promoted_memory);
+}
+
+void ArrayBufferTracker::AccountForConcurrentlyFreedMemory() {
+  heap_->update_external_memory(
+      static_cast<int64_t>(concurrently_freed_.Value()));
+  concurrently_freed_.SetValue(0);
 }
 
 void ArrayBufferTracker::FreeDeadInNewSpace(Heap* heap) {
   DCHECK_EQ(heap->gc_state(), Heap::HeapState::SCAVENGE);
   for (Page* page : NewSpacePageRange(heap->new_space()->FromSpaceStart(),
                                       heap->new_space()->FromSpaceEnd())) {
     bool empty = ProcessBuffers(page, kUpdateForwardedRemoveOthers);
     CHECK(empty);
   }
-  heap->account_external_memory_concurrently_freed();
+  AccountForConcurrentlyFreedMemory();
 }
 
 void ArrayBufferTracker::FreeDead(Page* page) {
   // Callers need to ensure having the page lock.
   LocalArrayBufferTracker* tracker = page->local_tracker();
   if (tracker == nullptr) return;
   DCHECK(!page->SweepingDone());
-  tracker->Free<LocalArrayBufferTracker::kFreeDead>();
+  LocalArrayBufferTracker::ProcessResult result =
+      tracker->Free<LocalArrayBufferTracker::kFreeDead>();
+  if (page->InNewSpace()) {
+    retained_from_new_space_.Increment(-static_cast<intptr_t>(result.freed));
+  } else {
+    retained_from_old_space_.Increment(-static_cast<intptr_t>(result.freed));
+  }
   if (tracker->IsEmpty()) {
     page->ReleaseLocalTracker();
   }
 }
 
 void ArrayBufferTracker::FreeAll(Page* page) {
   LocalArrayBufferTracker* tracker = page->local_tracker();
   if (tracker == nullptr) return;
-  tracker->Free<LocalArrayBufferTracker::kFreeAll>();
+  LocalArrayBufferTracker::ProcessResult result =
+      tracker->Free<LocalArrayBufferTracker::kFreeAll>();
+  concurrently_freed_.Increment(static_cast<intptr_t>(result.freed));
+  if (page->InNewSpace()) {
+    retained_from_new_space_.Increment(-static_cast<intptr_t>(result.freed));
+  } else {
+    retained_from_old_space_.Increment(-static_cast<intptr_t>(result.freed));
+  }
   if (tracker->IsEmpty()) {
     page->ReleaseLocalTracker();
   }
 }
 
 bool ArrayBufferTracker::ProcessBuffers(Page* page, ProcessingMode mode) {
   LocalArrayBufferTracker* tracker = page->local_tracker();
   if (tracker == nullptr) return true;
 
   DCHECK(page->SweepingDone());
-  tracker->Process(
+  LocalArrayBufferTracker::ProcessResult result = tracker->Process(
       [mode](JSArrayBuffer* old_buffer, JSArrayBuffer** new_buffer) {
         MapWord map_word = old_buffer->map_word();
         if (map_word.IsForwardingAddress()) {
           *new_buffer = JSArrayBuffer::cast(map_word.ToForwardingAddress());
           return LocalArrayBufferTracker::kUpdateEntry;
         }
         return mode == kUpdateForwardedKeepOthers
                    ? LocalArrayBufferTracker::kKeepEntry
                    : LocalArrayBufferTracker::kRemoveEntry;
       });
+  concurrently_freed_.Increment(static_cast<intptr_t>(result.freed));
+  if (page->InNewSpace()) {
+    retained_from_new_space_.Increment(

[Michael Lippautz, 2016/08/04 11:50:02]

General: When (and if) https://codereview.chromium.org/2215693002/ lands, we can
write this much nicer, staying completely in size_t land.

[Hannes Payer (out of office), 2016/08/05 12:14:13]

Nice, please do that.

[Michael Lippautz, 2016/08/08 08:34:46]

Done.

+        -(static_cast<intptr_t>(result.freed) +
+          static_cast<intptr_t>(result.promoted)));
+  } else {
+    retained_from_old_space_.Increment(-static_cast<intptr_t>(result.freed));
+  }
+  retained_from_old_space_.Increment(static_cast<intptr_t>(result.promoted));
   return tracker->IsEmpty();
 }
 
 bool ArrayBufferTracker::IsTracked(JSArrayBuffer* buffer) {
   Page* page = Page::FromAddress(buffer->address());
   {
     base::LockGuard<base::Mutex> guard(page->mutex());
     LocalArrayBufferTracker* tracker = page->local_tracker();
     if (tracker == nullptr) return false;
     return tracker->IsTracked(buffer);
   }
 }
 
 }  // namespace internal
 }  // namespace v8