[heap] Removing marking step size ramp-up interval heuristic.

The heuristic is no longer needed now that we have concurrent marking.

Bug: chromium:834371
Change-Id: I8ca3eaacdab618f690d8007aff66713260ace19f
Reviewed-on: https://chromium-review.googlesource.com/1017123Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52693}

src/heap/heap.cc

@@ -2247,7 +2247,7 @@ void Heap::ComputeFastPromotionMode(double survival_rate) {
       !FLAG_optimize_for_size && FLAG_fast_promotion_new_space &&
       !ShouldReduceMemory() && new_space_->IsAtMaximumCapacity() &&
       survived_in_new_space >= kMinPromotedPercentForFastPromotionMode;
-  if (FLAG_trace_gc_verbose) {
+  if (FLAG_trace_gc_verbose && !FLAG_trace_gc_ignore_scavenger) {
     PrintIsolate(
         isolate(), "Fast promotion mode: %s survival rate: %" PRIuS "%%\n",
         fast_promotion_mode_ ? "true" : "false", survived_in_new_space);

src/heap/incremental-marking.cc

@@ -952,10 +952,6 @@ size_t IncrementalMarking::StepSizeToKeepUpWithAllocations() {
 }
 
 size_t IncrementalMarking::StepSizeToMakeProgress() {
-  // We increase step size gradually based on the time passed in order to
-  // leave marking work to standalone tasks. The ramp up duration and the
-  // target step count are chosen based on benchmarks.
-  const int kRampUpIntervalMs = 300;
   const size_t kTargetStepCount = 256;
   const size_t kTargetStepCountAtOOM = 32;
   size_t oom_slack = heap()->new_space()->Capacity() + 64 * MB;
@@ -964,12 +960,8 @@ size_t IncrementalMarking::StepSizeToMakeProgress() {
     return heap()->PromotedSpaceSizeOfObjects() / kTargetStepCountAtOOM;
   }
 
-  size_t step_size = Max(initial_old_generation_size_ / kTargetStepCount,
-                         IncrementalMarking::kMinStepSizeInBytes);
-  double time_passed_ms =
-      heap_->MonotonicallyIncreasingTimeInMs() - start_time_ms_;
-  double factor = Min(time_passed_ms / kRampUpIntervalMs, 1.0);
-  return static_cast<size_t>(factor * step_size);
+  return Max(initial_old_generation_size_ / kTargetStepCount,
+             IncrementalMarking::kMinStepSizeInBytes);
 }
 
 void IncrementalMarking::AdvanceIncrementalMarkingOnAllocation() {