Introduce a new growth criterion for the new space behind a flag

With this flag, we grow if more than 10% survived the last scavenge.

BUG=none
R=hpayer@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/753543002

Cr-Commit-Position: refs/heads/master@{#25540}

src/flag-definitions.h

@@ -537,6 +537,9 @@ DEFINE_INT(max_semi_space_size, 0,
            "max size of a semi-space (in MBytes), the new space consists of two"
            "semi-spaces")
 DEFINE_INT(semi_space_growth_factor, 2, "factor by which to grow the new space")
+DEFINE_BOOL(experimental_new_space_growth_heuristic, false,
+            "Grow the new space based on the percentage of survivors instead "
+            "of their absolute value.")
 DEFINE_INT(max_old_space_size, 0, "max size of the old space (in Mbytes)")
 DEFINE_INT(max_executable_size, 0, "max size of executable memory (in Mbytes)")
 DEFINE_BOOL(gc_global, false, "always perform global GCs")

src/heap/heap.cc

@@ -70,6 +70,7 @@ Heap::Heap()
       // generation can be aligned to its size.
       maximum_committed_(0),
       survived_since_last_expansion_(0),
+      survived_last_scavenge_(0),
       sweep_generation_(0),
       always_allocate_scope_depth_(0),
       contexts_disposed_(0),
@@ -1301,11 +1302,18 @@ static void VerifyNonPointerSpacePointers(Heap* heap) {
 
 
 void Heap::CheckNewSpaceExpansionCriteria() {
+  if (FLAG_experimental_new_space_growth_heuristic) {
     if (new_space_.TotalCapacity() < new_space_.MaximumCapacity() &&
+        survived_last_scavenge_ * 100 / new_space_.TotalCapacity() >= 10) {
+      // Grow the size of new space if there is room to grow, and more than 10%
+      // have survived the last scavenge.
+      new_space_.Grow();
+      survived_since_last_expansion_ = 0;
+    }
+  } else if (new_space_.TotalCapacity() < new_space_.MaximumCapacity() &&
              survived_since_last_expansion_ > new_space_.TotalCapacity()) {
-    // Grow the size of new space if there is room to grow, enough data
-    // has survived scavenge since the last expansion and we are not in
-    // high promotion mode.
+    // Grow the size of new space if there is room to grow, and enough data
+    // has survived scavenge since the last expansion.
     new_space_.Grow();
     survived_since_last_expansion_ = 0;
   }

src/heap/heap.h

@@ -1195,6 +1195,7 @@ class Heap {
 
   inline void IncrementYoungSurvivorsCounter(int survived) {
     DCHECK(survived >= 0);
+    survived_last_scavenge_ = survived;
     survived_since_last_expansion_ += survived;
   }
 
@@ -1506,6 +1507,9 @@ class Heap {
   // scavenge since last new space expansion.
   int survived_since_last_expansion_;
 
+  // ... and since the last scavenge.
+  int survived_last_scavenge_;
+
   // For keeping track on when to flush RegExp code.
   int sweep_generation_;