Add memory pressure notification API

src/heap/heap.h

 // Copyright 2012 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_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
 // Clients of this interface shouldn't depend on lots of heap internals.
 // Do not include anything from src/heap here!
+#include "include/v8.h"
 #include "src/allocation.h"
 #include "src/assert-scope.h"
 #include "src/atomic-utils.h"
 #include "src/globals.h"
 #include "src/heap-symbols.h"
 // TODO(mstarzinger): Two more includes to kill!
 #include "src/heap/spaces.h"
 #include "src/heap/store-buffer.h"
 #include "src/list.h"
 
 namespace v8 {
 namespace internal {
 
+using v8::MemoryPressureLevel;
+
 // Defines all the roots in Heap.
 #define STRONG_ROOT_LIST(V)                                                    \
   V(Map, byte_array_map, ByteArrayMap)                                         \
   V(Map, free_space_map, FreeSpaceMap)                                         \
   V(Map, one_pointer_filler_map, OnePointerFillerMap)                          \
   V(Map, two_pointer_filler_map, TwoPointerFillerMap)                          \
   /* Cluster the most popular ones in a few cache lines here at the top.    */ \
   V(Smi, store_buffer_top, StoreBufferTop)                                     \
   V(Oddball, undefined_value, UndefinedValue)                                  \
   V(Oddball, the_hole_value, TheHoleValue)                                     \
@@ skipping 693 matching lines @@
   //
   // Support for the API.
   //
 
   void CreateApiObjects();
 
   // Implements the corresponding V8 API function.
   bool IdleNotification(double deadline_in_seconds);
   bool IdleNotification(int idle_time_in_ms);
 
+  void MemoryPressureNotification(MemoryPressureLevel level,
+                                  bool is_isolate_locked);
+
   double MonotonicallyIncreasingTimeInMs();
 
   void RecordStats(HeapStats* stats, bool take_snapshot = false);
 
   // Check new space expansion criteria and expand semispaces if it was hit.
   void CheckNewSpaceExpansionCriteria();
 
   inline bool HeapIsFullEnoughToStartIncrementalMarking(intptr_t limit) {
     if (FLAG_stress_compaction && (gc_count_ & 1) != 0) return true;
 
     intptr_t adjusted_allocation_limit = limit - new_space_.Capacity();
 
     if (PromotedTotalSize() >= adjusted_allocation_limit) return true;
 
+    if (memory_pressure_level_.Value() != MemoryPressureLevel::kNone)
+      return true;
+
     return false;
   }
 
   void VisitExternalResources(v8::ExternalResourceVisitor* visitor);
 
   // An object should be promoted if the object has survived a
   // scavenge operation.
   inline bool ShouldBePromoted(Address old_address, int object_size);
 
   void ClearNormalizedMapCaches();
@@ skipping 63 matching lines @@
                           int size_in_bytes);
 
   bool deserialization_complete() const { return deserialization_complete_; }
 
   bool HasLowAllocationRate();
   bool HasHighFragmentation();
   bool HasHighFragmentation(intptr_t used, intptr_t committed);
 
   void SetOptimizeForLatency() { optimize_for_memory_usage_ = false; }
   void SetOptimizeForMemoryUsage();
-  bool ShouldOptimizeForMemoryUsage() { return optimize_for_memory_usage_; }
+  bool ShouldOptimizeForMemoryUsage() {
+    return optimize_for_memory_usage_ ||
+           memory_pressure_level_.Value() != MemoryPressureLevel::kNone;
+  }
 
   // ===========================================================================
   // Initialization. ===========================================================
   // ===========================================================================
 
   // Configure heap size in MB before setup. Return false if the heap has been
   // set up already.
   bool ConfigureHeap(int max_semi_space_size, int max_old_space_size,
                      int max_executable_size, size_t code_range_size);
   bool ConfigureHeapDefault();
@@ skipping 1142 matching lines @@
   // scavenge since last new space expansion.
   intptr_t survived_since_last_expansion_;
 
   // ... and since the last scavenge.
   intptr_t survived_last_scavenge_;
 
   // This is not the depth of nested AlwaysAllocateScope's but rather a single
   // count, as scopes can be acquired from multiple tasks (read: threads).
   AtomicNumber<size_t> always_allocate_scope_count_;
 
+  AtomicValue<MemoryPressureLevel> memory_pressure_level_;

[Hannes Payer (out of office), 2016/03/18 13:27:26]

For completeness, add a comment to describe that field.

[ulan, 2016/03/18 16:10:00]

Done.

+
   // For keeping track of context disposals.
   int contexts_disposed_;
 
   // The length of the retained_maps array at the time of context disposal.
   // This separates maps in the retained_maps array that were created before
   // and after context disposal.
   int number_of_disposed_maps_;
 
   int global_ic_age_;
 
@@ skipping 625 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_