Lower limit for external allocation and improve tracing.

R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/16896012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15210 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap-inl.h

@@ -550,7 +550,7 @@ intptr_t Heap::AdjustAmountOfExternalAllocatedMemory(
     if (amount >= 0) {
       amount_of_external_allocated_memory_ = amount;
     } else {
-      // Give up and reset the counters in case of an overflow.
+      // Give up and reset the counters in case of an underflow.
       amount_of_external_allocated_memory_ = 0;
       amount_of_external_allocated_memory_at_last_global_gc_ = 0;
     }
@@ -558,8 +558,11 @@ intptr_t Heap::AdjustAmountOfExternalAllocatedMemory(
   if (FLAG_trace_external_memory) {
     PrintPID("%8.0f ms: ", isolate()->time_millis_since_init());
     PrintF("Adjust amount of external memory: delta=%6" V8_PTR_PREFIX "d KB, "
-           " amount=%6" V8_PTR_PREFIX "d KB, isolate=0x%08" V8PRIxPTR ".\n",
-           change_in_bytes / 1024, amount_of_external_allocated_memory_ / 1024,
+           "amount=%6" V8_PTR_PREFIX "d KB, since_gc=%6" V8_PTR_PREFIX "d KB, "
+           "isolate=0x%08" V8PRIxPTR ".\n",
+           change_in_bytes / KB,
+           amount_of_external_allocated_memory_ / KB,
+           PromotedExternalMemorySize() / KB,
            reinterpret_cast<intptr_t>(isolate()));
   }
   ASSERT(amount_of_external_allocated_memory_ >= 0);

src/heap.cc

@@ -6645,7 +6645,12 @@ bool Heap::ConfigureHeap(int max_semispace_size,
   max_semispace_size_ = RoundUpToPowerOf2(max_semispace_size_);
   reserved_semispace_size_ = RoundUpToPowerOf2(reserved_semispace_size_);
   initial_semispace_size_ = Min(initial_semispace_size_, max_semispace_size_);
-  external_allocation_limit_ = 16 * max_semispace_size_;
+
+  // The external allocation limit should be below 256 MB on all architectures
+  // to avoid unnecessary low memory notifications, as that is the threshold
+  // for some embedders.
+  external_allocation_limit_ = 12 * max_semispace_size_;
+  ASSERT(external_allocation_limit_ <= 256 * MB);
 
   // The old generation is paged and needs at least one page for each space.
   int paged_space_count = LAST_PAGED_SPACE - FIRST_PAGED_SPACE + 1;