Reland "[heap] Fine-grained JSArrayBuffer 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/heap.h"
 #include "src/isolate.h"
+#include "src/objects-inl.h"
 #include "src/objects.h"
-#include "src/objects-inl.h"
 #include "src/v8.h"
 
 namespace v8 {
 namespace internal {
 
-ArrayBufferTracker::~ArrayBufferTracker() {
-  Isolate* isolate = heap()->isolate();
+LocalArrayBufferTracker::~LocalArrayBufferTracker() {
   size_t freed_memory = 0;
-  for (auto& buffer : live_array_buffers_) {
-    isolate->array_buffer_allocator()->Free(buffer.first, buffer.second);
-    freed_memory += buffer.second;
+  for (auto& buffer : array_buffers_) {
+    heap_->isolate()->array_buffer_allocator()->Free(buffer.second.first,
+                                                     buffer.second.second);
+    freed_memory += buffer.second.second;
   }
-  for (auto& buffer : live_array_buffers_for_scavenge_) {
-    isolate->array_buffer_allocator()->Free(buffer.first, buffer.second);
-    freed_memory += buffer.second;
+  if (freed_memory > 0) {
+    heap_->update_amount_of_external_allocated_freed_memory(
+        static_cast<intptr_t>(freed_memory));
   }
-  live_array_buffers_.clear();
-  live_array_buffers_for_scavenge_.clear();
-  not_yet_discovered_array_buffers_.clear();
-  not_yet_discovered_array_buffers_for_scavenge_.clear();
+  array_buffers_.clear();
+}
 
+void LocalArrayBufferTracker::Add(Key key, const Value& value) {
+  array_buffers_[key] = value;
+}
+
+LocalArrayBufferTracker::Value LocalArrayBufferTracker::Remove(Key key) {
+  DCHECK_EQ(array_buffers_.count(key), 1);
+  Value value = array_buffers_[key];
+  array_buffers_.erase(key);
+  return value;
+}
+
+void LocalArrayBufferTracker::FreeDead() {

[Hannes Payer (out of office), 2016/06/01 13:44:17]

DCHECK that the page of the array buffer was not swept, i.e. we are in a state
where we still have liveness information.

[Michael Lippautz, 2016/06/01 14:19:19]

Done (... in the caller where we still have access to the page).

+  size_t freed_memory = 0;
+  for (TrackingMap::iterator it = array_buffers_.begin();
+       it != array_buffers_.end();) {
+    if (Marking::IsWhite(Marking::MarkBitFrom(it->first))) {
+      heap_->isolate()->array_buffer_allocator()->Free(it->second.first,
+                                                       it->second.second);
+      freed_memory += it->second.second;
+      array_buffers_.erase(it++);
+    } else {
+      it++;
+    }
+  }
   if (freed_memory > 0) {
-    heap()->update_amount_of_external_allocated_memory(
-        -static_cast<int64_t>(freed_memory));
+    heap_->update_amount_of_external_allocated_freed_memory(
+        static_cast<intptr_t>(freed_memory));
   }
 }
 
+template <typename Callback>
+void LocalArrayBufferTracker::Process(Callback callback) {
+  JSArrayBuffer* new_buffer = nullptr;
+  size_t freed_memory = 0;
+  for (TrackingMap::iterator it = array_buffers_.begin();
+       it != array_buffers_.end();) {
+    switch (callback(it->first, &new_buffer)) {
+      case kKeepEntry:
+        it++;
+        break;
+      case kUpdateEntry:
+        DCHECK_NOT_NULL(new_buffer);
+        Page::FromAddress(new_buffer->address())
+            ->local_tracker<Page::kCreateIfNotPresent>()
+            ->Add(new_buffer, it->second);
+        array_buffers_.erase(it++);
+        break;
+      case kRemoveEntry:
+        heap_->isolate()->array_buffer_allocator()->Free(it->second.first,
+                                                         it->second.second);
+        freed_memory += it->second.second;
+        array_buffers_.erase(it++);
+        break;
+      default:
+        UNREACHABLE();
+    }
+  }
+  if (freed_memory > 0) {
+    heap_->update_amount_of_external_allocated_freed_memory(
+        static_cast<intptr_t>(freed_memory));
+  }
+}
 
-void ArrayBufferTracker::RegisterNew(JSArrayBuffer* buffer) {
+void ArrayBufferTracker::RegisterNew(Heap* heap, JSArrayBuffer* buffer) {
   void* data = buffer->backing_store();
   if (!data) return;
 
-  bool in_new_space = heap()->InNewSpace(buffer);
-  size_t length = NumberToSize(heap()->isolate(), buffer->byte_length());
-  if (in_new_space) {
-    live_array_buffers_for_scavenge_[data] = length;
-  } else {
-    live_array_buffers_[data] = length;
+  size_t length = NumberToSize(heap->isolate(), buffer->byte_length());
+  Page* page = Page::FromAddress(buffer->address());
+  LocalArrayBufferTracker* tracker =
+      page->local_tracker<Page::kCreateIfNotPresent>();
+  DCHECK_NOT_NULL(tracker);
+  {
+    base::LockGuard<base::Mutex> guard(page->mutex());
+    tracker->Add(buffer, std::make_pair(data, length));
   }
-
   // We may go over the limit of externally allocated memory here. We call the
   // api function to trigger a GC in this case.
-  reinterpret_cast<v8::Isolate*>(heap()->isolate())
+  reinterpret_cast<v8::Isolate*>(heap->isolate())
       ->AdjustAmountOfExternalAllocatedMemory(length);
 }
 
-
-void ArrayBufferTracker::Unregister(JSArrayBuffer* buffer) {
+void ArrayBufferTracker::Unregister(Heap* heap, JSArrayBuffer* buffer) {
   void* data = buffer->backing_store();
   if (!data) return;
 
-  bool in_new_space = heap()->InNewSpace(buffer);
-  std::map<void*, size_t>* live_buffers =
-      in_new_space ? &live_array_buffers_for_scavenge_ : &live_array_buffers_;
-  std::map<void*, size_t>* not_yet_discovered_buffers =
-      in_new_space ? &not_yet_discovered_array_buffers_for_scavenge_
-                   : &not_yet_discovered_array_buffers_;
-
-  DCHECK(live_buffers->count(data) > 0);
-
-  size_t length = (*live_buffers)[data];
-  live_buffers->erase(data);
-  not_yet_discovered_buffers->erase(data);
-
-  heap()->update_amount_of_external_allocated_memory(
-      -static_cast<int64_t>(length));
+  Page* page = Page::FromAddress(buffer->address());
+  LocalArrayBufferTracker* tracker = page->local_tracker<Page::kDontCreate>();
+  DCHECK_NOT_NULL(tracker);
+  size_t length = 0;
+  {
+    base::LockGuard<base::Mutex> guard(page->mutex());
+    length = tracker->Remove(buffer).second;
+  }
+  heap->update_amount_of_external_allocated_memory(
+      -static_cast<intptr_t>(length));
 }
 
+void ArrayBufferTracker::FreeDeadInNewSpace(Heap* heap) {
+  NewSpacePageIterator from_it(heap->new_space()->FromSpaceStart(),
+                               heap->new_space()->FromSpaceEnd());
+  while (from_it.has_next()) {
+    ProcessBuffers(from_it.next(), kUpdateForwardedRemoveOthers);
+  }
+  heap->account_amount_of_external_allocated_freed_memory();
+}
 
-void ArrayBufferTracker::MarkLive(JSArrayBuffer* buffer) {
-  base::LockGuard<base::Mutex> guard(&mutex_);
-  void* data = buffer->backing_store();
-
-  // ArrayBuffer might be in the middle of being constructed.
-  if (data == heap()->undefined_value()) return;
-  if (heap()->InNewSpace(buffer)) {
-    not_yet_discovered_array_buffers_for_scavenge_.erase(data);
-  } else {
-    not_yet_discovered_array_buffers_.erase(data);
+void ArrayBufferTracker::FreeDead(Page* page) {
+  // Only called from the sweeper, which already holds the page lock.
+  LocalArrayBufferTracker* tracker = page->local_tracker<Page::kDontCreate>();
+  if (tracker == nullptr) return;
+  tracker->FreeDead();
+  if (tracker->IsEmpty()) {
+    page->ReleaseLocalTracker();
   }
 }
 
-
-void ArrayBufferTracker::FreeDead(bool from_scavenge) {
-  size_t freed_memory = 0;
-  Isolate* isolate = heap()->isolate();
-  for (auto& buffer : not_yet_discovered_array_buffers_for_scavenge_) {
-    isolate->array_buffer_allocator()->Free(buffer.first, buffer.second);
-    freed_memory += buffer.second;
-    live_array_buffers_for_scavenge_.erase(buffer.first);
+void ArrayBufferTracker::ProcessBuffers(Page* page, ProcessingMode mode) {
+  LocalArrayBufferTracker* tracker = page->local_tracker<Page::kDontCreate>();
+  if (tracker == nullptr) return;
+  {
+    base::LockGuard<base::Mutex> guard(page->mutex());
+    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;
+        });
   }
-
-  if (!from_scavenge) {
-    for (auto& buffer : not_yet_discovered_array_buffers_) {
-      isolate->array_buffer_allocator()->Free(buffer.first, buffer.second);
-      freed_memory += buffer.second;
-      live_array_buffers_.erase(buffer.first);
-    }
-  }
-
-  not_yet_discovered_array_buffers_for_scavenge_ =
-      live_array_buffers_for_scavenge_;
-  if (!from_scavenge) not_yet_discovered_array_buffers_ = live_array_buffers_;
-
-  // Do not call through the api as this code is triggered while doing a GC.
-  heap()->update_amount_of_external_allocated_memory(
-      -static_cast<int64_t>(freed_memory));
 }
 
-
-void ArrayBufferTracker::PrepareDiscoveryInNewSpace() {
-  not_yet_discovered_array_buffers_for_scavenge_ =
-      live_array_buffers_for_scavenge_;
-}
-
-
-void ArrayBufferTracker::Promote(JSArrayBuffer* buffer) {
-  base::LockGuard<base::Mutex> guard(&mutex_);
-
-  if (buffer->is_external()) return;
-  void* data = buffer->backing_store();
-  if (!data) return;
-  // ArrayBuffer might be in the middle of being constructed.
-  if (data == heap()->undefined_value()) return;
-  DCHECK(live_array_buffers_for_scavenge_.count(data) > 0);
-  live_array_buffers_[data] = live_array_buffers_for_scavenge_[data];
-  live_array_buffers_for_scavenge_.erase(data);
-  not_yet_discovered_array_buffers_for_scavenge_.erase(data);
+bool ArrayBufferTracker::IsTracked(JSArrayBuffer* buffer) {
+  Page* page = Page::FromAddress(buffer->address());
+  LocalArrayBufferTracker* tracker =
+      page->local_tracker<Page::kCreateIfNotPresent>();
+  {
+    base::LockGuard<base::Mutex> guard(page->mutex());
+    return tracker->IsTracked(buffer);
+  }
 }
 
 }  // namespace internal
 }  // namespace v8