Report the reason for a garbage collection when verbose GC is enabled.

runtime/vm/heap.cc

Index: runtime/vm/heap.cc
diff --git a/runtime/vm/heap.cc b/runtime/vm/heap.cc
index 6c9a7d1d858613cd89848ffcb6d9fb2edb4d0101..08fd72acbd203360f36087b5d99f8c20d6a74564 100644
--- a/runtime/vm/heap.cc
+++ b/runtime/vm/heap.cc
@@ -178,17 +178,17 @@ void Heap::CollectGarbage(Space space, ApiCallbacks api_callbacks) {
   bool invoke_api_callbacks = (api_callbacks == kInvokeApiCallbacks);
   switch (space) {
     case kNew:
-      new_space_->Scavenge(invoke_api_callbacks);
+      new_space_->Scavenge(invoke_api_callbacks, "new space");
       if (new_space_->HadPromotionFailure()) {
-        old_space_->MarkSweep(true);
+        old_space_->MarkSweep(true, "promotion failure");
       }
       break;
     case kOld:
-      old_space_->MarkSweep(invoke_api_callbacks);
+      old_space_->MarkSweep(invoke_api_callbacks, "old space");
       break;
     case kCode:
       UNIMPLEMENTED();
-      code_space_->MarkSweep(invoke_api_callbacks);
+      code_space_->MarkSweep(invoke_api_callbacks, "code space");

[siva, 2012/08/27 16:54:49]

Can we list these reasons in heap.h as static const char* fields. That way we
would have one spot to look for all reasons and people would not put some random
strings (lower case/upper case/missing spaces etc).

e.g:
static const char* new_space_full_ = "new space full";

and use Heap::new_space_full() in the code.

I think the strings could be a little more verbose
e.g "new space exhausted" instead of just "new space"

[Ivan Posva, 2012/08/27 22:04:23]

I like the suggestion of having the different reasons be collected in a central
place, but I am not sure they need to be more verbose.

       break;
     default:
       UNREACHABLE();
@@ -211,10 +211,10 @@ void Heap::CollectGarbage(Space space) {
 
 
 void Heap::CollectAllGarbage() {
-  new_space_->Scavenge(kInvokeApiCallbacks);
-  old_space_->MarkSweep(kInvokeApiCallbacks);
+  new_space_->Scavenge(kInvokeApiCallbacks, "full");
+  old_space_->MarkSweep(kInvokeApiCallbacks, "full");
   // TODO(iposva): Merge old and code space.
-  // code_space_->MarkSweep(kInvokeApiCallbacks);
+  // code_space_->MarkSweep(kInvokeApiCallbacks, "full");
   if (FLAG_verbose_gc) {
     PrintSizes();
   }