Add flag to control profiler rate

runtime/vm/profiler.cc

 // Copyright (c) 2013, 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.
 
 #include <cstdio>
 
 #include "platform/utils.h"
 
 #include "vm/atomic.h"
 #include "vm/isolate.h"
@@ skipping 19 matching lines @@
 
 #if defined(USING_SIMULATOR) || defined(TARGET_OS_WINDOWS) || \
     defined(TARGET_OS_MACOS) || defined(TARGET_OS_ANDROID)
   DEFINE_FLAG(bool, profile, false, "Enable Sampling Profiler");
 #else
   DEFINE_FLAG(bool, profile, true, "Enable Sampling Profiler");
 #endif
 DEFINE_FLAG(bool, trace_profiled_isolates, false, "Trace profiled isolates.");
 DEFINE_FLAG(charp, profile_dir, NULL,
             "Enable writing profile data into specified directory.");
+DEFINE_FLAG(int, profile_period, 1000,
+            "Time between profiler samples in microseconds. Minimum 250.");
 
 bool Profiler::initialized_ = false;
 Monitor* Profiler::monitor_ = NULL;
 SampleBuffer* Profiler::sample_buffer_ = NULL;
 
 void Profiler::InitOnce() {
+  const int kMinimumProfilePeriod = 250;
   if (!FLAG_profile) {
     return;
   }
   ASSERT(!initialized_);
   initialized_ = true;
   monitor_ = new Monitor();
   sample_buffer_ = new SampleBuffer();
   NativeSymbolResolver::InitOnce();
   ThreadInterrupter::InitOnce();
+  if (FLAG_profile_period < kMinimumProfilePeriod) {
+    FLAG_profile_period = kMinimumProfilePeriod;
+  }
+  ThreadInterrupter::SetInterruptPeriod(FLAG_profile_period);
 }
 
 
 void Profiler::Shutdown() {
   if (!FLAG_profile) {
     return;
   }
   ASSERT(initialized_);
   ThreadInterrupter::Shutdown();
   NativeSymbolResolver::ShutdownOnce();
@@ skipping 462 matching lines @@
     return false;
   }
   uintptr_t cursor = reinterpret_cast<uintptr_t>(fp);
   cursor += sizeof(fp);
   bool r = cursor >= lower_bound_ && cursor < stack_upper_;
   return r;
 }
 
 
 }  // namespace dart