[heap] inline allocation steps refactor

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 "src/allocation.h"
 #include "src/atomic-utils.h"
 #include "src/base/atomicops.h"
@@ skipping 2458 matching lines @@
 
 class NewSpace : public Space {
  public:
   // Constructor.
   explicit NewSpace(Heap* heap)
       : Space(heap, NEW_SPACE, NOT_EXECUTABLE),
         to_space_(heap, kToSpace),
         from_space_(heap, kFromSpace),
         reservation_(),
         inline_allocation_limit_step_(0),
+        incremental_marking_step_(0),
+        idle_scavenge_step_(0),
         top_on_previous_step_(0) {}
 
   // Sets up the new space using the given chunk.
   bool SetUp(int reserved_semispace_size_, int max_semi_space_size);
 
   // Tears down the space.  Heap memory was not allocated by the space, so it
   // is not deallocated here.
   void TearDown();
 
   // True if the space has been set up but not torn down.
@@ skipping 153 matching lines @@
   MUST_USE_RESULT INLINE(
       AllocationResult AllocateRawUnaligned(int size_in_bytes));
 
   MUST_USE_RESULT INLINE(AllocationResult AllocateRaw(
       int size_in_bytes, AllocationAlignment alignment));
 
   // Reset the allocation pointer to the beginning of the active semispace.
   void ResetAllocationInfo();
 
   void UpdateInlineAllocationLimit(int size_in_bytes);
-  void LowerInlineAllocationLimit(intptr_t step) {
-    inline_allocation_limit_step_ = step;
-    UpdateInlineAllocationLimit(0);
-    top_on_previous_step_ = step ? allocation_info_.top() : 0;
+
+  void SetIncrementalMarkingStep(intptr_t step) {
+    incremental_marking_step_ = step;
+    LowerInlineAllocationLimit();
+  }
+  void SetIdleScavengeStep(intptr_t step) {
+    idle_scavenge_step_ = step;
+    LowerInlineAllocationLimit();
   }
 
   // Get the extent of the inactive semispace (for use as a marking stack,
   // or to zap it). Notice: space-addresses are not necessarily on the
   // same page, so FromSpaceStart() might be above FromSpaceEnd().
   Address FromSpacePageLow() { return from_space_.page_low(); }
   Address FromSpacePageHigh() { return from_space_.page_high(); }
   Address FromSpaceStart() { return from_space_.space_start(); }
   Address FromSpaceEnd() { return from_space_.space_end(); }
 
@@ skipping 55 matching lines @@
   }
 
   bool IsFromSpaceCommitted() { return from_space_.is_committed(); }
 
   SemiSpace* active_space() { return &to_space_; }
 
  private:
   // Update allocation info to match the current to-space page.
   void UpdateAllocationInfo();
 
+  void LowerInlineAllocationLimit() {
+    intptr_t step;
+    if (incremental_marking_step_ && idle_scavenge_step_) {
+      step = Min(incremental_marking_step_, idle_scavenge_step_);
+    } else {
+      step = incremental_marking_step_ ? incremental_marking_step_
+                                       : idle_scavenge_step_;
+    }
+    inline_allocation_limit_step_ = step;
+    top_on_previous_step_ = step ? allocation_info_.top() : 0;
+    UpdateInlineAllocationLimit(0);
+  }
+
   Address chunk_base_;
   uintptr_t chunk_size_;
 
   // The semispaces.
   SemiSpace to_space_;
   SemiSpace from_space_;
   base::VirtualMemory reservation_;
   int pages_used_;
 
   // Start address and bit mask for containment testing.
   Address start_;
   uintptr_t address_mask_;
   uintptr_t object_mask_;
   uintptr_t object_expected_;
 
   // Allocation pointer and limit for normal allocation and allocation during
   // mark-compact collection.
   AllocationInfo allocation_info_;
 
-  // When incremental marking is active we will set allocation_info_.limit
-  // to be lower than actual limit and then will gradually increase it
-  // in steps to guarantee that we do incremental marking steps even
-  // when all allocation is performed from inlined generated code.
+  // When inline allocation stepping is active, either because of incremental
+  // marking or because of idle scavenge, we 'interrupt' inline allocation every
+  // once in a while. This is done by setting allocation_info_.limit to be lower
+  // than the actual limit and and increasing it in steps to guarantee that the
+  // observers are notified periodically.
   intptr_t inline_allocation_limit_step_;

[Hannes Payer (out of office), 2015/10/13 16:51:24]

Having a state that belongs to incremental marking or scavenging in spaces is
not nice. I would prefer to keep the abstract value of allocation limit in
spaces and handle actual setting on a higher level.

With this approach, each customer would need its own step counter. That does not
really scale.

+  intptr_t incremental_marking_step_;
+  intptr_t idle_scavenge_step_;
 
   Address top_on_previous_step_;
 
   HistogramInfo* allocated_histogram_;
   HistogramInfo* promoted_histogram_;
 
   bool EnsureAllocation(int size_in_bytes, AllocationAlignment alignment);
 
   // If we are doing inline allocation in steps, this method performs the 'step'
-  // operation. Right now incremental marking is the only consumer of inline
-  // allocation steps. top is the memory address of the bump pointer at the last
+  // operation. top is the memory address of the bump pointer at the last
   // inline allocation (i.e. it determines the numbers of bytes actually
   // allocated since the last step.) new_top is the address of the bump pointer
   // where the next byte is going to be allocated from. top and new_top may be
   // different when we cross a page boundary or reset the space.
   void InlineAllocationStep(Address top, Address new_top);
 
   friend class SemiSpaceIterator;
 };
 
 // -----------------------------------------------------------------------------
@@ skipping 233 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_