[heap] Use smaller minimum allocation limit growing step when optimizing for memory usage.

BUG=chromium:634900

Review-Url: https://codereview.chromium.org/2223493002
Cr-Commit-Position: refs/heads/master@{#38435}

src/heap/heap.cc

@@ -2014,7 +2014,7 @@ void Heap::UnregisterArrayBuffer(JSArrayBuffer* buffer) {
 void Heap::ConfigureInitialOldGenerationSize() {
   if (!old_generation_size_configured_ && tracer()->SurvivalEventsRecorded()) {
     old_generation_allocation_limit_ =
-        Max(kMinimumOldGenerationAllocationLimit,
+        Max(MinimumAllocationLimitGrowingStep(),
             static_cast<intptr_t>(
                 static_cast<double>(old_generation_allocation_limit_) *
                 (tracer()->AverageSurvivalRatio() / 100)));
@@ -5151,7 +5151,7 @@ intptr_t Heap::CalculateOldGenerationAllocationLimit(double factor,
   CHECK(factor > 1.0);
   CHECK(old_gen_size > 0);
   intptr_t limit = static_cast<intptr_t>(old_gen_size * factor);
-  limit = Max(limit, old_gen_size + kMinimumOldGenerationAllocationLimit);
+  limit = Max(limit, old_gen_size + MinimumAllocationLimitGrowingStep());
   limit += new_space_.Capacity();
   intptr_t halfway_to_the_max = (old_gen_size + max_old_generation_size_) / 2;
   return Min(limit, halfway_to_the_max);

src/heap/heap.h

@@ -519,9 +519,6 @@ class Heap {
   };
   typedef List<Chunk> Reservation;
 
-  static const intptr_t kMinimumOldGenerationAllocationLimit =
-      8 * (Page::kPageSize > MB ? Page::kPageSize : MB);
-
   static const int kInitalOldGenerationLimitFactor = 2;
 
 #if V8_OS_ANDROID
@@ -1803,6 +1800,15 @@ class Heap {
   void SetOldGenerationAllocationLimit(intptr_t old_gen_size, double gc_speed,
                                        double mutator_speed);
 
+  intptr_t MinimumAllocationLimitGrowingStep() {
+    const double kRegularAllocationLimitGrowingStep = 8;
+    const double kLowMemoryAllocationLimitGrowingStep = 2;
+    intptr_t limit = (Page::kPageSize > MB ? Page::kPageSize : MB);
+    return limit * (ShouldOptimizeForMemoryUsage()
+                        ? kLowMemoryAllocationLimitGrowingStep
+                        : kRegularAllocationLimitGrowingStep);
+  }
+
   // ===========================================================================
   // Idle notification. ========================================================
   // ===========================================================================

test/mjsunit/regress/regress-crbug-500497.js

@@ -4,6 +4,7 @@
 
 // New space must be at max capacity to trigger pretenuring decision.
 // Flags: --allow-natives-syntax --verify-heap --max-semi-space-size=1
+// Flags: --expose-gc
 
 var global = [];  // Used to keep some objects alive.
 
@@ -12,6 +13,8 @@ function Ctor() {
   return result;
 }
 
+gc();
+
 for (var i = 0; i < 120; i++) {
   // Make the "a" property long-lived, while everything else is short-lived.
   global.push(Ctor().a);