Add kGCCallbackFlagCollectAllExternalMemory for external memory limit triggered gc

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 69bf17c33e5c901609e76e4af509c970cac5aab5..539bd410b1cf06c2063861c9a442605525d527c4 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -5238,6 +5238,7 @@ enum GCCallbackFlags {
   kGCCallbackFlagForced = 1 << 2,
   kGCCallbackFlagSynchronousPhantomCallbackProcessing = 1 << 3,
   kGCCallbackFlagCollectAllAvailableGarbage = 1 << 4,
+  kGCCallbackFlagCollectAllExternalMemory = 1 << 5,
 };
 
 typedef void (*GCCallback)(GCType type, GCCallbackFlags flags);
@@ -8794,11 +8795,14 @@ int64_t Isolate::AdjustAmountOfExternalAllocatedMemory(
   typedef internal::Internals I;
   int64_t* external_memory = reinterpret_cast<int64_t*>(
       reinterpret_cast<uint8_t*>(this) + I::kExternalMemoryOffset);
-  const int64_t external_memory_limit = *reinterpret_cast<int64_t*>(
+  int64_t* external_memory_limit = reinterpret_cast<int64_t*>(
       reinterpret_cast<uint8_t*>(this) + I::kExternalMemoryLimitOffset);
   const int64_t amount = *external_memory + change_in_bytes;
   *external_memory = amount;
-  if (change_in_bytes > 0 && amount > external_memory_limit) {
+  if (amount + 192 * 1024 * 1024 < *external_memory_limit) {

[Michael Lippautz, 2016/08/12 07:06:23]

Can we avoid polluting the API and instead adjust the external_memory_limit from
within V8?

The fast check here should merely be a comparison of a counter against a limit.

+    *external_memory_limit = amount + 192 * 1024 * 1024;

[Hannes Payer (out of office), 2016/08/12 14:06:09]

Why are you shrinking the limit here?

+  }
+  if (change_in_bytes > 0 && amount > *external_memory_limit) {
     ReportExternalAllocationLimitReached();
   }
   return *external_memory;