Reduce CPU usage when no isolates need to be profiled.

runtime/include/dart_api.h

Index: runtime/include/dart_api.h
diff --git a/runtime/include/dart_api.h b/runtime/include/dart_api.h
index 7aded5027f53762f4a97d5039e2c0becbd363390..2a2b2f4bf4acba4f4b07fba3793f629434dc6840 100755
--- a/runtime/include/dart_api.h
+++ b/runtime/include/dart_api.h
@@ -2624,6 +2624,25 @@ DART_EXPORT Dart_Handle Dart_SetPeer(Dart_Handle object, void* peer);
 
 
 /*
+ * ========
+ * Profiler
+ * ========
+ */
+
+/**
+ * Disables profiler interrupts for the current isolate. Repeated calls to
+ * Dart_BlockProfiler are allowed but must be paired with the same number of
+ * calls to Dart_UnblockProfiler to unblock the profiler.
+ */
+DART_EXPORT void Dart_BlockProfiler();

[Ivan Posva, 2014/05/25 12:25:16]

This is not just related to the profiler. What we want is to signal the VM that
this isolate is making a blocking call. => Dart_IsolateBlocked,
Dart_IsolateUnblocked

The profiler then certainly can key off of this information, but there might be
other areas that could use this signal.

[Anders Johnsen, 2014/05/25 18:36:34]

+1, I like the more generic IsolateBlocked/IsolateUnblocked.

[Cutch, 2014/05/26 06:59:35]

Done.

+
+/**
+ * Re-enables profiler interrupts for the current isolate.
+ */
+DART_EXPORT void Dart_UnblockProfiler();
+
+
+/*
  * =======
  * Service
  * =======