Fix for issue 25954.

runtime/vm/pages.cc

Index: runtime/vm/pages.cc
diff --git a/runtime/vm/pages.cc b/runtime/vm/pages.cc
index 2f894b53a2bfc9ed7c7710aed1d831533190203f..f96f737d7fe7e923d8141615fef2b5b9c514cf04 100644
--- a/runtime/vm/pages.cc
+++ b/runtime/vm/pages.cc
@@ -1166,7 +1166,8 @@ void PageSpaceController::EvaluateGarbageCollection(
       before.used_in_words - last_usage_.used_in_words;
   intptr_t garbage = before.used_in_words - after.used_in_words;

[zra, 2016/08/08 14:59:37]

const

ASSERT(garbage >= 0);

[siva, 2016/08/11 17:32:48]

Done.

   double k = garbage / static_cast<double>(allocated_since_previous_gc);

[zra, 2016/08/08 14:59:37]

const

[siva, 2016/08/11 17:32:48]

Done.

-  heap_->RecordData(PageSpace::kGarbageRatio, static_cast<int>(k * 100));
+  int garbage_ratio = static_cast<int>(k * 100);

[zra, 2016/08/08 14:59:37]

const intptr_t

[siva, 2016/08/11 17:32:48]

Added const, change to intptr_t would be coupled with the change above if
needed.

+  heap_->RecordData(PageSpace::kGarbageRatio, garbage_ratio);
 
   // Define GC to be 'worthwhile' iff at least fraction t of heap is garbage.
   double t = 1.0 - desired_utilization_;
@@ -1175,16 +1176,39 @@ void PageSpaceController::EvaluateGarbageCollection(
     t += (gc_time_fraction - garbage_collection_time_ratio_) / 100.0;
   }
 
-  // Find minimum 'grow_heap_' such that after increasing capacity by
-  // 'grow_heap_' pages and filling them, we expect a GC to be worthwhile.
-  for (grow_heap_ = 0; grow_heap_ < heap_growth_max_; ++grow_heap_) {
-    intptr_t limit =
-        after.capacity_in_words + (grow_heap_ * PageSpace::kPageSizeInWords);
-    intptr_t allocated_before_next_gc = limit - after.used_in_words;
-    double estimated_garbage = k * allocated_before_next_gc;
-    if (t <= estimated_garbage / limit) {
-      break;
+  if (garbage_ratio == 0) {
+    // No garbage in the previous cycle so it would be hard to compute a
+    // grow_heap_ size based on estimated garbage so we use growth ratio
+    // instead.
+    intptr_t grow_ratio =

[zra, 2016/08/08 14:59:37]

const

[siva, 2016/08/11 17:32:48]

Done.

+        (static_cast<intptr_t>(after.capacity_in_words / t) -
+         after.capacity_in_words) / PageSpace::kPageSizeInWords;
+    grow_heap_ = heap_growth_max_;
+    grow_heap_ = Utils::Maximum(grow_heap_, grow_ratio);

[zra, 2016/08/08 14:59:37]

grow_heap_ = Utils::Maximum(heap_growth_max_, grow_ratio);

[siva, 2016/08/11 17:32:48]

Done but had to introduce a static_cast as heap_growth_max_ is an 'int'

+  } else {
+    // Find minimum 'grow_heap_' such that after increasing capacity by
+    // 'grow_heap_' pages and filling them, we expect a GC to be worthwhile.
+    intptr_t max = heap_growth_max_;
+    intptr_t min = 0;
+    intptr_t adjustment = 0;
+    // Find minimum 'grow_heap_' such that after increasing capacity by

[zra, 2016/08/08 14:59:37]

Duplicated comment

[siva, 2016/08/11 17:32:48]

Removed duplicate.

+    // 'grow_heap_' pages and filling them, we expect a GC to be worthwhile.
+    grow_heap_ = 0;
+    while (min < max) {
+      grow_heap_ = (max + min) / 2;
+      intptr_t limit =

[zra, 2016/08/08 14:59:37]

const

[siva, 2016/08/11 17:32:48]

Done.

+          after.capacity_in_words + (grow_heap_ * PageSpace::kPageSizeInWords);
+      intptr_t allocated_before_next_gc = limit - after.used_in_words;

[zra, 2016/08/08 14:59:37]

const

[siva, 2016/08/11 17:32:48]

Done.

+      double estimated_garbage = k * allocated_before_next_gc;

[zra, 2016/08/08 14:59:37]

const

[siva, 2016/08/11 17:32:48]

Done.

+      if (t <= estimated_garbage / limit) {
+        max = grow_heap_ - 1;
+        adjustment = -1;
+      } else {
+        min = grow_heap_ + 1;
+        adjustment = 1;
+      }
     }
+    grow_heap_ += adjustment;
   }
   heap_->RecordData(PageSpace::kPageGrowth, grow_heap_);