[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..f94d01ed0d67f08f5e613a08045b2291a3e6df28 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -2476,6 +2476,8 @@ class NewSpace : public Space {
         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.
@@ -2649,10 +2651,14 @@ class NewSpace : public Space {
   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,
@@ -2728,6 +2734,19 @@ class NewSpace : public Space {
   // 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_;
 
@@ -2747,11 +2766,14 @@ 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_;

[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_;
 
@@ -2761,8 +2783,7 @@ 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