[heap] inline allocation steps refactor

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index 69a8d89fccba5c5aa06f91d2a1995870b70ef033..01676397b96d65272ea741c18dd5f77e1a798b79 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -2461,6 +2461,42 @@ class NewSpacePageIterator BASE_EMBEDDED {
 };
 
 
+class InlineAllocationObserver {

[Hannes Payer (out of office), 2015/10/16 15:31:17]

This class needs a description and a few comments. And since it is
unit-testable, can we add a few unit tests.

[ofrobots, 2015/10/16 21:26:35]

Done.

+ public:
+  typedef void (*callback_t)(int bytes_allocated, void* arg);
+
+  InlineAllocationObserver(intptr_t step_size, callback_t callback,
+                           void* callback_arg)
+      : step_size_(step_size),
+        callback_(callback),
+        callback_arg_(callback_arg),
+        bytes_to_next_step_(step_size) {
+    DCHECK(step_size > 0);
+  }
+
+  InlineAllocationObserver(const InlineAllocationObserver&) = default;
+  InlineAllocationObserver& operator=(const InlineAllocationObserver&) =
+      default;
+
+  void step(int bytes_allocated) {
+    bytes_to_next_step_ -= bytes_allocated;
+    if (bytes_to_next_step_ <= 0) {
+      callback_(static_cast<int>(step_size_ - bytes_to_next_step_),
+                callback_arg_);
+      bytes_to_next_step_ = step_size_;
+    }
+  }
+
+  intptr_t step_size() const { return step_size_; }
+  callback_t callback() const { return callback_; }
+
+ private:
+  intptr_t step_size_;
+  callback_t callback_;
+  void* callback_arg_;
+  intptr_t bytes_to_next_step_;
+};
+
 // -----------------------------------------------------------------------------
 // The young generation space.
 //
@@ -2649,10 +2685,16 @@ class NewSpace : public Space {
   void ResetAllocationInfo();
 
   void UpdateInlineAllocationLimit(int size_in_bytes);
-  void LowerInlineAllocationLimit(intptr_t step) {
-    inline_allocation_limit_step_ = step;
+
+  void AddInlineAllocationObserver(
+      intptr_t step_size, InlineAllocationObserver::callback_t callback,
+      void* callback_arg);
+  void RemoveInlineAllocationObserver(
+      InlineAllocationObserver::callback_t callback);
+  void DisableInlineAllocationSteps() {
+    inline_allocation_limit_step_ = 0;
+    top_on_previous_step_ = 0;
     UpdateInlineAllocationLimit(0);
-    top_on_previous_step_ = step ? allocation_info_.top() : 0;
   }
 
   // Get the extent of the inactive semispace (for use as a marking stack,
@@ -2728,6 +2770,8 @@ class NewSpace : public Space {
   // Update allocation info to match the current to-space page.
   void UpdateAllocationInfo();
 
+  void UpdateInlineAllocationLimitStep();
+
   Address chunk_base_;
   uintptr_t chunk_size_;
 
@@ -2747,11 +2791,13 @@ class NewSpace : public Space {
   // 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_;
+  List<InlineAllocationObserver> inline_allocation_observers_;
 
   Address top_on_previous_step_;
 
@@ -2761,8 +2807,7 @@ class NewSpace : public Space {
   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