Reduce CPU usage when no isolates need to be profiled.

runtime/include/dart_api.h

 /*
  * Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
  * for details. All rights reserved. Use of this source code is governed by a
  * BSD-style license that can be found in the LICENSE file.
  */
 
 #ifndef INCLUDE_DART_API_H_
 #define INCLUDE_DART_API_H_
 
 /** \mainpage Dart Embedding API Reference
@@ skipping 2606 matching lines @@
  * \param object An object.
  * \param peer A value to store in the peer field.
  *
  * \return Returns an error if 'object' is a subtype of Null, num, or
  *   bool.
  */
 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
  * =======
  */
 
 /**
  * Returns the Service isolate initialized and with the dart:vmservice library
  * loaded and booted.
  *
  * This will call the embedder provided Dart_ServiceIsolateCreateCalback to
@@ skipping 77 matching lines @@
  * NOTE: If multiple callbacks with the same name are registered, only the
  * last callback registered will be remembered.
  */
 DART_EXPORT void Dart_RegisterRootServiceRequestCallback(
     const char* name,
     Dart_ServiceRequestCallback callback,
     void* user_data);
 
 
 #endif  /* INCLUDE_DART_API_H_ */  /* NOLINT */