[heap] New API for increasing the heap limit for debugging.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 6e5d788bd1d3644b0d0deb13a8f117ab63c91c42..303895de816316d14ca71d96b0c9a4ed4637abfb 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -950,6 +950,22 @@ class Heap {
     return memory_pressure_level_.Value() != MemoryPressureLevel::kNone;
   }
 
+  void IncreaseHeapLimitForDebugging() {
+    const size_t kDebugHeapSizeFactor = 4;
+    size_t max_limit = std::numeric_limits<size_t>::max() / 4;
+    max_old_generation_size_ =
+        Max(max_old_generation_size_,
+            Min(max_limit, max_old_generation_size_ * kDebugHeapSizeFactor));

[Hannes Payer (out of office), 2016/12/22 11:50:29]

Isn't the requirement on 32-bit to stay within 2G to support dev tools?

[ulan, 2016/12/22 14:04:51]

Yes, max_limit is 1GB on 32-bit.

+  }
+
+  void RestoreOriginalHeapLimit() {
+    // Do not set the limit lower than the live size + some slack.
+    size_t min_limit = SizeOfObjects() + SizeOfObjects() / 4;

[Hannes Payer (out of office), 2016/12/22 11:50:29]

If the restoring of the initial max_old_generation_size_ fails, we are going to
run now with a larger max size. Is that a problem?

[ulan, 2016/12/22 14:04:51]

Yep, we have no choice there. It is probably ok, because the increase is
requested by the user in devtools.

[Hannes Payer (out of office), 2016/12/23 07:49:56]

We could try to set it at the end of a full gc and retry until we reached the
original maximum. Do you think that makes sense?

[ulan, 2016/12/27 12:41:35]

It makes sense as mitigation, but there is no guarantee that GC can reduce heap
to the original maximum. Let's for now keep it simple :)

+    max_old_generation_size_ =
+        Min(max_old_generation_size_,
+            Max(initial_max_old_generation_size_, min_limit));
+  }
+
   // ===========================================================================
   // Initialization. ===========================================================
   // ===========================================================================
@@ -2131,6 +2147,7 @@ class Heap {
   size_t max_semi_space_size_;
   size_t initial_semispace_size_;
   size_t max_old_generation_size_;
+  size_t initial_max_old_generation_size_;
   size_t initial_old_generation_size_;
   bool old_generation_size_configured_;
   size_t max_executable_size_;