1    :  // Copyright 2014 Google Inc. All Rights Reserved.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  
  15    :  #ifndef SYZYGY_SAMPLER_SAMPLING_PROFILER_H_
  16    :  #define SYZYGY_SAMPLER_SAMPLING_PROFILER_H_
  17    :  
  18    :  #include <vector>
  19    :  
  20    :  #include "base/time/time.h"
  21    :  #include "base/win/scoped_handle.h"
  22    :  
  23    :  namespace sampler {
  24    :  
  25    :  // This class exposes the functionality of Window's built-in sampling profiler.
  26    :  // Each profiler instance covers a range of memory, and while the profiler is
  27    :  // running, its buckets will count the number of times the instruction counter
  28    :  // lands in the associated range of memory on a sample.
  29    :  // The sampling interval is settable, but the setting is system-wide.
  30    :  class SamplingProfiler {
  31    :   public:
  32    :    // Create an uninitialized sampling profiler.
  33    :    SamplingProfiler();
  34    :    ~SamplingProfiler();
  35    :  
  36    :    // Initializes the profiler to cover the memory range |start| through
  37    :    // |start| + |size|, in the process |process_handle| with bucket size
  38    :    // |2^log2_bucket_size|, |log2_bucket_size| must be in the range 2-31,
  39    :    // for bucket sizes of 4 bytes to 2 gigabytes.
  40    :    // The process handle must grant at least PROCESS_QUERY_INFORMATION.
  41    :    // The memory range should be exectuable code, like e.g. the text segment
  42    :    // of an exectuable (whether DLL or EXE).
  43    :    // Returns true on success.
  44    :    bool Initialize(HANDLE process_handle,
  45    :                    void* start,
  46    :                    size_t size,
  47    :                    size_t log2_bucket_size);
  48    :  
  49    :    // Start this profiler, which must be initialized and not started.
  50    :    bool Start();
  51    :    // Stop this profiler, which must be started.
  52    :    bool Stop();
  53    :  
  54    :    // Get and set the sampling interval.
  55    :    // Note that this is a system-wide setting.
  56    :    static bool SetSamplingInterval(base::TimeDelta sampling_interval);
  57    :    static bool GetSamplingInterval(base::TimeDelta* sampling_interval);
  58    :  
  59    :    // Accessors.
  60    :    bool is_started() const { return is_started_; }
  61    :  
  62    :    // It is safe to read the counts in the sampling buckets at any time.
  63    :    // Note however that there's no guarantee that you'll read consistent counts
  64    :    // until the profiler has been stopped, as the counts may be updating on other
  65    :    // CPU cores.
  66  E :    const std::vector<ULONG>& buckets() const { return buckets_; }
  67    :  
  68    :   private:
  69    :    // Handle to the corresponding kernel object.
  70    :    base::win::ScopedHandle profile_handle_;
  71    :    // True iff this profiler is started.
  72    :    bool is_started_;
  73    :    std::vector<ULONG> buckets_;
  74    :  
  75    :    DISALLOW_COPY_AND_ASSIGN(SamplingProfiler);
  76    :  };
  77    :  
  78    :  }  // namespace sampler
  79    :  
  80    :  #endif  // SYZYGY_SAMPLER_SAMPLING_PROFILER_H_