[heap] Don't unmap new space pages while sweeping is active

src/heap/spaces.h

 // Copyright 2011 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.
 
 #ifndef V8_HEAP_SPACES_H_
 #define V8_HEAP_SPACES_H_
 
 #include <list>
 #include <memory>
 #include <unordered_set>
@@ skipping 1187 matching lines @@
       kRegular,     // Pages of kPageSize that do not live in a CodeRange and
                     // can thus be used for stealing.
       kNonRegular,  // Large chunks and executable chunks.
       kPooled,      // Pooled chunks, already uncommited and ready for reuse.
       kNumberOfChunkQueues,
     };
 
     template <ChunkQueueType type>
     void AddMemoryChunkSafe(MemoryChunk* chunk) {
       base::LockGuard<base::Mutex> guard(&mutex_);
-      chunks_[type].push_back(chunk);
+      if (type != kRegular || allocator_->CanFreeMemoryChunk(chunk)) {
+        chunks_[type].push_back(chunk);
+      } else {
+        DCHECK_EQ(type, kRegular);
+        delayed_regular_chunks_.push_back(chunk);
+      }
     }
 
     template <ChunkQueueType type>
     MemoryChunk* GetMemoryChunkSafe() {
       base::LockGuard<base::Mutex> guard(&mutex_);
       if (chunks_[type].empty()) return nullptr;
       MemoryChunk* chunk = chunks_[type].front();
       chunks_[type].pop_front();
       return chunk;
     }
 
+    void ReconsiderDelayedChunks();
     void PerformFreeMemoryOnQueuedChunks();
 
     base::Mutex mutex_;
     MemoryAllocator* allocator_;
     std::list<MemoryChunk*> chunks_[kNumberOfChunkQueues];
+    // Delayed chunks cannot be processed in the current unmapping cycle because
+    // of dependencies. See MemoryAllocator::CanFreeMemoryChunk.

[Hannes Payer (out of office), 2016/08/18 09:38:42]

Just spell out the "dependencies" here.

[Michael Lippautz, 2016/08/18 09:59:40]

Done.

+    std::list<MemoryChunk*> delayed_regular_chunks_;
     base::Semaphore pending_unmapping_tasks_semaphore_;
     intptr_t concurrent_unmapping_tasks_active_;
 
     friend class MemoryAllocator;
   };
 
   enum AllocationMode {
     kRegular,
     kPooled,
   };
@@ skipping 18 matching lines @@
   template <MemoryAllocator::AllocationMode alloc_mode = kRegular,
             typename SpaceType>
   Page* AllocatePage(intptr_t size, SpaceType* owner, Executability executable);
 
   LargePage* AllocateLargePage(intptr_t size, LargeObjectSpace* owner,
                                Executability executable);
 
   template <MemoryAllocator::FreeMode mode = kFull>
   void Free(MemoryChunk* chunk);
 
+  bool CanFreeMemoryChunk(MemoryChunk* chunk);
+
   // Returns allocated spaces in bytes.
   intptr_t Size() { return size_.Value(); }
 
   // Returns allocated executable spaces in bytes.
   intptr_t SizeExecutable() { return size_executable_.Value(); }
 
   // Returns the maximum available bytes of heaps.
   intptr_t Available() {
     intptr_t size = Size();
     return capacity_ < size ? 0 : capacity_ - size;
@@ skipping 1756 matching lines @@
     count = 0;
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_SPACES_H_