[heap] Scale max heap growing factor.

src/heap/heap.cc

 // Copyright 2012 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.
 
 #include "src/heap/heap.h"
 
 #include <unordered_map>
 #include <unordered_set>
 
 #include "src/accessors.h"
@@ skipping 4175 matching lines @@
 bool Heap::HasHighFragmentation(size_t used, size_t committed) {
   const size_t kSlack = 16 * MB;
   // Fragmentation is high if committed > 2 * used + kSlack.
   // Rewrite the exression to avoid overflow.
   DCHECK_GE(committed, used);
   return committed - used > used + kSlack;
 }
 
 bool Heap::ShouldOptimizeForMemoryUsage() {
   return FLAG_optimize_for_size || isolate()->IsIsolateInBackground() ||
-         HighMemoryPressure() || IsLowMemoryDevice();
+         HighMemoryPressure();
 }
 
 void Heap::ActivateMemoryReducerIfNeeded() {
   // Activate memory reducer when switching to background if
   // - there was no mark compact since the start.
   // - the committed memory can be potentially reduced.
   // 2 pages for the old, code, and map space + 1 page for new space.
   const int kMinCommittedMemory = 7 * Page::kPageSize;
   if (ms_count_ == 0 && CommittedMemory() > kMinCommittedMemory &&
       isolate()->IsIsolateInBackground()) {
@@ skipping 1217 matching lines @@
 //   (Limit - Live) / mutator_speed = Limit * MU / (gc_speed * (1 - MU))
 //   (Limit - Live) = Limit * MU * mutator_speed / (gc_speed * (1 - MU))
 // substitute R = gc_speed / mutator_speed
 //   (Limit - Live) = Limit * MU  / (R * (1 - MU))
 // substitute F = Limit / Live
 //   F - 1 = F * MU  / (R * (1 - MU))
 //   F - F * MU / (R * (1 - MU)) = 1
 //   F * (1 - MU / (R * (1 - MU))) = 1
 //   F * (R * (1 - MU) - MU) / (R * (1 - MU)) = 1
 //   F = R * (1 - MU) / (R * (1 - MU) - MU)
-double Heap::HeapGrowingFactor(double gc_speed, double mutator_speed) {
-  if (gc_speed == 0 || mutator_speed == 0) return kMaxHeapGrowingFactor;
+double Heap::HeapGrowingFactor(double gc_speed, double mutator_speed,
+                               double max_factor) {
+  DCHECK(max_factor >= kMinHeapGrowingFactor);
+  DCHECK(max_factor <= kMaxHeapGrowingFactor);
+  if (gc_speed == 0 || mutator_speed == 0) return max_factor;
 
   const double speed_ratio = gc_speed / mutator_speed;
   const double mu = kTargetMutatorUtilization;
 
   const double a = speed_ratio * (1 - mu);
   const double b = speed_ratio * (1 - mu) - mu;
 
   // The factor is a / b, but we need to check for small b first.
-  double factor =
-      (a < b * kMaxHeapGrowingFactor) ? a / b : kMaxHeapGrowingFactor;
-  factor = Min(factor, kMaxHeapGrowingFactor);
+  double factor = (a < b * max_factor) ? a / b : max_factor;
+  factor = Min(factor, max_factor);
   factor = Max(factor, kMinHeapGrowingFactor);
   return factor;
 }
 
+double Heap::MaxHeapGrowingFactor(size_t max_old_generation_size) {
+  const double min_small_factor = 1.3;
+  const double max_small_factor = 2.0;
+  const double high_factor = 4.0;
+
+  size_t max_old_generation_size_in_mb = max_old_generation_size / MB;
+  max_old_generation_size_in_mb =
+      Max(max_old_generation_size_in_mb,
+          static_cast<size_t>(kMinOldGenerationSize));
+
+  // If we are on a device with lots of memory, we allow a high heap
+  // growing factor.
+  if (max_old_generation_size_in_mb == kMaxOldGenerationSize) {

[ulan, 2017/06/09 08:39:43]

Should it be >= instead of == ?

[Hannes Payer (out of office), 2017/06/09 12:16:47]

Done.

+    return high_factor;
+  }
+
+  DCHECK_GE(max_old_generation_size_in_mb, kMinOldGenerationSize);
+  DCHECK_LT(max_old_generation_size_in_mb, kMaxOldGenerationSize);
+
+  // On smaller devices we linearly scale the factor: (X-A)/(B-A)*(D-C)+C
+  double factor = (max_old_generation_size_in_mb - kMinOldGenerationSize) *
+                      (max_small_factor - min_small_factor) /
+                      (kMaxOldGenerationSize - 1 - kMinOldGenerationSize) +

[ulan, 2017/06/09 08:39:43]

Why (-1) here?

[Hannes Payer (out of office), 2017/06/09 12:16:47]

I decided to do that because we would never reach the 2.0 case otherwise. For
simplicity, I am happy to remove it.

+                  min_small_factor;
+  return factor;
+}
+
 size_t Heap::CalculateOldGenerationAllocationLimit(double factor,
                                                    size_t old_gen_size) {
   CHECK(factor > 1.0);
   CHECK(old_gen_size > 0);
   uint64_t limit = static_cast<uint64_t>(old_gen_size * factor);
   limit = Max(limit, static_cast<uint64_t>(old_gen_size) +
                          MinimumAllocationLimitGrowingStep());
   limit += new_space_->Capacity();
   uint64_t halfway_to_the_max =
       (static_cast<uint64_t>(old_gen_size) + max_old_generation_size_) / 2;
   return static_cast<size_t>(Min(limit, halfway_to_the_max));
 }
 
 size_t Heap::MinimumAllocationLimitGrowingStep() {
   const size_t kRegularAllocationLimitGrowingStep = 8;
   const size_t kLowMemoryAllocationLimitGrowingStep = 2;
   size_t limit = (Page::kPageSize > MB ? Page::kPageSize : MB);
   return limit * (ShouldOptimizeForMemoryUsage()
                       ? kLowMemoryAllocationLimitGrowingStep
                       : kRegularAllocationLimitGrowingStep);
 }
 
 void Heap::SetOldGenerationAllocationLimit(size_t old_gen_size, double gc_speed,
                                            double mutator_speed) {
-  double factor = HeapGrowingFactor(gc_speed, mutator_speed);
+  double max_factor = MaxHeapGrowingFactor(max_old_generation_size_);
+  double factor = HeapGrowingFactor(gc_speed, mutator_speed, max_factor);
 
   if (FLAG_trace_gc_verbose) {
     isolate_->PrintWithTimestamp(
         "Heap growing factor %.1f based on mu=%.3f, speed_ratio=%.f "
         "(gc=%.f, mutator=%.f)\n",
         factor, kTargetMutatorUtilization, gc_speed / mutator_speed, gc_speed,
         mutator_speed);
   }
 
-  if (IsMemoryConstrainedDevice()) {
-    factor = Min(factor, kMaxHeapGrowingFactorMemoryConstrained);
-  }
-
   if (memory_reducer_->ShouldGrowHeapSlowly() ||
       ShouldOptimizeForMemoryUsage()) {
     factor = Min(factor, kConservativeHeapGrowingFactor);
   }
 
   if (FLAG_stress_compaction || ShouldReduceMemory()) {
     factor = kMinHeapGrowingFactor;
   }
 
   if (FLAG_heap_growing_percent > 0) {
     factor = 1.0 + FLAG_heap_growing_percent / 100.0;
   }
 
   old_generation_allocation_limit_ =
       CalculateOldGenerationAllocationLimit(factor, old_gen_size);
 
   if (FLAG_trace_gc_verbose) {
     isolate_->PrintWithTimestamp(
         "Grow: old size: %" PRIuS " KB, new limit: %" PRIuS " KB (%.1f)\n",
         old_gen_size / KB, old_generation_allocation_limit_ / KB, factor);
   }
 }
 
 void Heap::DampenOldGenerationAllocationLimit(size_t old_gen_size,
                                               double gc_speed,
                                               double mutator_speed) {
-  double factor = HeapGrowingFactor(gc_speed, mutator_speed);
+  double max_factor = MaxHeapGrowingFactor(max_old_generation_size_);
+  double factor = HeapGrowingFactor(gc_speed, mutator_speed, max_factor);
   size_t limit = CalculateOldGenerationAllocationLimit(factor, old_gen_size);
   if (limit < old_generation_allocation_limit_) {
     if (FLAG_trace_gc_verbose) {
       isolate_->PrintWithTimestamp(
           "Dampen: old size: %" PRIuS " KB, old limit: %" PRIuS
           " KB, "
           "new limit: %" PRIuS " KB (%.1f)\n",
           old_gen_size / KB, old_generation_allocation_limit_ / KB, limit / KB,
           factor);
     }
@@ skipping 1081 matching lines @@
     case LO_SPACE:
       return "LO_SPACE";
     default:
       UNREACHABLE();
   }
   return NULL;
 }
 
 }  // namespace internal
 }  // namespace v8