Make the speed of incrmental marking depend also on the rate

src/incremental-marking.cc

Index: src/incremental-marking.cc
===================================================================
--- src/incremental-marking.cc	(revision 12583)
+++ src/incremental-marking.cc	(working copy)
@@ -52,7 +52,7 @@
       steps_count_since_last_gc_(0),
       steps_took_since_last_gc_(0),
       should_hurry_(false),
-      allocation_marking_factor_(0),
+      marking_speed_(0),
       allocated_(0),
       no_marking_scope_depth_(0) {
 }
@@ -81,17 +81,19 @@
                                              Object* value,
                                              Isolate* isolate) {
   ASSERT(obj->IsHeapObject());
+  IncrementalMarking* marking = isolate->heap()->incremental_marking();
+  ASSERT(!marking->is_compacting_);
 
-  // Fast cases should already be covered by RecordWriteStub.
-  ASSERT(value->IsHeapObject());
-  ASSERT(!value->IsHeapNumber());
-  ASSERT(!value->IsString() ||
-         value->IsConsString() ||
-         value->IsSlicedString());
-  ASSERT(Marking::IsWhite(Marking::MarkBitFrom(HeapObject::cast(value))));
+  MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
+  int counter = chunk->write_barrier_counter();
+  if (counter < (MemoryChunk::kWriteBarrierCounterGranularity / 2)) {
+    marking->write_barriers_invoked_since_last_step_ +=
+        MemoryChunk::kWriteBarrierCounterGranularity -
+            chunk->write_barrier_counter();
+    chunk->set_write_barrier_counter(
+        MemoryChunk::kWriteBarrierCounterGranularity);
+  }
 
-  IncrementalMarking* marking = isolate->heap()->incremental_marking();
-  ASSERT(!marking->is_compacting_);
   marking->RecordWrite(obj, NULL, value);
 }
 
@@ -99,8 +101,20 @@
 void IncrementalMarking::RecordWriteForEvacuationFromCode(HeapObject* obj,
                                                           Object** slot,
                                                           Isolate* isolate) {
+  ASSERT(obj->IsHeapObject());
   IncrementalMarking* marking = isolate->heap()->incremental_marking();
   ASSERT(marking->is_compacting_);
+
+  MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
+  int counter = chunk->write_barrier_counter();
+  if (counter < (MemoryChunk::kWriteBarrierCounterGranularity / 2)) {
+    marking->write_barriers_invoked_since_last_step_ +=
+        MemoryChunk::kWriteBarrierCounterGranularity -
+            chunk->write_barrier_counter();
+    chunk->set_write_barrier_counter(
+        MemoryChunk::kWriteBarrierCounterGranularity);
+  }
+
   marking->RecordWrite(obj, slot, *slot);
 }
 
@@ -504,7 +518,7 @@
     state_ = SWEEPING;
   }
 
-  heap_->new_space()->LowerInlineAllocationLimit(kAllocatedThreshold);
+  heap_->new_space()->LowerInlineAllocationLimit(kIncrementalMarkingThreshold);
 }
 
 
@@ -773,11 +787,24 @@
 
   allocated_ += allocated_bytes;
 
-  if (allocated_ < kAllocatedThreshold) return;
+  if (allocated_ < kIncrementalMarkingThreshold &&
+      write_barriers_invoked_since_last_step_ < kIncrementalMarkingThreshold) {

[Michael Starzinger, 2012/09/26 08:06:38]

Even if the two thresholds we are comparing against happen to have the same
value, I think we should still use two different constants here (one for
allocation and one for WB counts).

+    return;
+  }
 
   if (state_ == MARKING && no_marking_scope_depth_ > 0) return;
 
-  intptr_t bytes_to_process = allocated_ * allocation_marking_factor_;
+  // The marking speed is driven either by the allocation rate or by the rate
+  // at which we are having to check the color of objects in the write barrier.
+  // It is possible for a tight non-allocating loop to run a lot of write
+  // barriers before we get here and check them (marking can only take place on
+  // allocation), so to reduce the lumpiness we don't use the write barriers
+  // invoked since last step directly to determine the amount of work to do.
+  intptr_t bytes_to_process =
+      marking_speed_ * Max(allocated_, kIncrementalMarkingThreshold);
+  allocated_ = 0;
+  write_barriers_invoked_since_last_step_ = 0;
+
   bytes_scanned_ += bytes_to_process;
 
   double start = 0;
@@ -832,17 +859,15 @@
     if (marking_deque_.IsEmpty()) MarkingComplete(action);
   }
 
-  allocated_ = 0;
-
   steps_count_++;
   steps_count_since_last_gc_++;
 
   bool speed_up = false;
 
-  if ((steps_count_ % kAllocationMarkingFactorSpeedupInterval) == 0) {
+  if ((steps_count_ % kMarkingSpeedAccellerationInterval) == 0) {
     if (FLAG_trace_gc) {
       PrintPID("Speed up marking after %d steps\n",
-               static_cast<int>(kAllocationMarkingFactorSpeedupInterval));
+               static_cast<int>(kMarkingSpeedAccellerationInterval));
     }
     speed_up = true;
   }
@@ -851,7 +876,7 @@
       (old_generation_space_available_at_start_of_incremental_ < 10 * MB);
 
   bool only_1_nth_of_space_that_was_available_still_left =
-      (SpaceLeftInOldSpace() * (allocation_marking_factor_ + 1) <
+      (SpaceLeftInOldSpace() * (marking_speed_ + 1) <
           old_generation_space_available_at_start_of_incremental_);
 
   if (space_left_is_very_small ||
@@ -862,7 +887,7 @@
 
   bool size_of_old_space_multiplied_by_n_during_marking =
       (heap_->PromotedTotalSize() >
-       (allocation_marking_factor_ + 1) *
+       (marking_speed_ + 1) *
            old_generation_space_used_at_start_of_incremental_);
   if (size_of_old_space_multiplied_by_n_during_marking) {
     speed_up = true;
@@ -873,7 +898,7 @@
 
   int64_t promoted_during_marking = heap_->PromotedTotalSize()
       - old_generation_space_used_at_start_of_incremental_;
-  intptr_t delay = allocation_marking_factor_ * MB;
+  intptr_t delay = marking_speed_ * MB;
   intptr_t scavenge_slack = heap_->MaxSemiSpaceSize();
 
   // We try to scan at at least twice the speed that we are allocating.
@@ -890,12 +915,12 @@
         PrintPID("Postponing speeding up marking until marking starts\n");
       }
     } else {
-      allocation_marking_factor_ += kAllocationMarkingFactorSpeedup;
-      allocation_marking_factor_ = static_cast<int>(
-          Min(kMaxAllocationMarkingFactor,
-              static_cast<intptr_t>(allocation_marking_factor_ * 1.3)));
+      marking_speed_ += kMarkingSpeedAccellerationInterval;
+      marking_speed_ = static_cast<int>(
+          Min(kMaxMarkingSpeed,
+              static_cast<intptr_t>(marking_speed_ * 1.3)));
       if (FLAG_trace_gc) {
-        PrintPID("Marking speed increased to %d\n", allocation_marking_factor_);
+        PrintPID("Marking speed increased to %d\n", marking_speed_);
       }
     }
   }
@@ -921,8 +946,9 @@
   steps_count_since_last_gc_ = 0;
   steps_took_since_last_gc_ = 0;
   bytes_rescanned_ = 0;
-  allocation_marking_factor_ = kInitialAllocationMarkingFactor;
+  marking_speed_ = kInitialMarkingSpeed;
   bytes_scanned_ = 0;
+  write_barriers_invoked_since_last_step_ = 0;
 }