Add flag to control number of stack frames collected by profiler

runtime/vm/profiler.h

 // 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.
 
 #ifndef VM_PROFILER_H_
 #define VM_PROFILER_H_
 
 #include "vm/allocation.h"
 #include "vm/code_observers.h"
 #include "vm/globals.h"
 #include "vm/thread.h"
 #include "vm/thread_interrupter.h"
 
 namespace dart {
 
 // Forward declarations.
 class JSONArray;
 class JSONStream;
 class ProfilerCodeRegionTable;
 struct Sample;
+class SampleBuffer;
 
 // Profiler
 class Profiler : public AllStatic {
  public:
   static void InitOnce();
   static void Shutdown();
 
   static void InitProfilingForIsolate(Isolate* isolate,
                                       bool shared_buffer = true);
   static void ShutdownProfilingForIsolate(Isolate* isolate);
@@ skipping 43 matching lines @@
   }
 
  private:
   SampleBuffer* sample_buffer_;
   bool own_sample_buffer_;
   DISALLOW_COPY_AND_ASSIGN(IsolateProfilerData);
 };
 
 
 // Profile sample.
 struct Sample {

[siva, 2014/01/16 23:34:23]

why not just make it class Sample ?

[Cutch, 2014/01/17 16:02:25]

Done.

-  static const intptr_t kNumStackFrames = 6;
   enum SampleType {
-    kIsolateStart,
-    kIsolateStop,
     kIsolateSample,
   };
+
   int64_t timestamp;
   ThreadId tid;
   Isolate* isolate;
-  uintptr_t pcs[kNumStackFrames];
   SampleType type;
   uint16_t vm_tags;
   uint16_t runtime_tags;
+  uintptr_t pcs[0];

[siva, 2014/01/16 23:34:23]

Document that this needs to be the last field, no fields should be added after
this.

[Cutch, 2014/01/17 16:02:25]

Done.

 
   void Init(SampleType type, Isolate* isolate, int64_t timestamp, ThreadId tid);
+  void CopyInto(Sample* dst) const;
+
+  static Sample* Allocate();
+  static intptr_t InstanceSize();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Sample);
 };
 
 
 // Ring buffer of samples.
 class SampleBuffer {
  public:
   static const intptr_t kDefaultBufferCapacity = 120000;  // 2 minutes @ 1000hz.
 
   explicit SampleBuffer(intptr_t capacity = kDefaultBufferCapacity);
   ~SampleBuffer();
 
   intptr_t capacity() const { return capacity_; }
-
   Sample* ReserveSample();
-
-  Sample GetSample(intptr_t i) const {
-    ASSERT(i >= 0);
-    ASSERT(i < capacity_);
-    return samples_[i];
-  }
+  void CopySample(intptr_t i, Sample* sample) const;
+  Sample* At(intptr_t idx) const;
 
  private:
   Sample* samples_;
   intptr_t capacity_;
   uintptr_t cursor_;
 
   DISALLOW_COPY_AND_ASSIGN(SampleBuffer);
 };
 
 
@@ skipping 22 matching lines @@
   const uintptr_t original_pc_;
   const uintptr_t original_fp_;
   const uintptr_t original_sp_;
   uintptr_t lower_bound_;
 };
 
 
 }  // namespace dart
 
 #endif  // VM_PROFILER_H_