base/win/sampling_profiler.h

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_WIN_SAMPLING_PROFILER_H_
   6 #define BASE_WIN_SAMPLING_PROFILER_H_
   7
   8 #include <vector>
   9
  10 #include "base/basictypes.h"
  11 #include "base/time.h"
  12 #include "base/win/scoped_handle.h"
  13
  14 namespace base {
  15 namespace win {
  16
  17 // This class exposes the functionality of Window's built-in sampling profiler.
  18 // Each profiler instance covers a range of memory, and while the profiler is
  19 // running, its buckets will count the number of times the instruction counter
  20 // lands in the associated range of memory on a sample.
  21 // The sampling interval is settable, but the setting is system-wide.
  22 class BASE_EXPORT SamplingProfiler {
  23  public:
  24   // Create an uninitialized sampling profiler.
  25   SamplingProfiler();
  26   ~SamplingProfiler();
  27
  28   // Initializes the profiler to cover the memory range |start| through
  29   // |start| + |size|, in the process |process_handle| with bucket size
  30   // |2^log2_bucket_size|, |log2_bucket_size| must be in the range 2-31,
  31   // for bucket sizes of 4 bytes to 2 gigabytes.
  32   // The process handle must grant at least PROCESS_QUERY_INFORMATION.
  33   // The memory range should be exectuable code, like e.g. the text segment
  34   // of an exectuable (whether DLL or EXE).
  35   // Returns true on success.
  36   bool Initialize(HANDLE process_handle,
  37                   void* start,
  38                   size_t size,
  39                   size_t log2_bucket_size);
  40
  41   // Start this profiler, which must be initialized and not started.
  42   bool Start();
  43   // Stop this profiler, which must be started.
  44   bool Stop();
  45
  46   // Get and set the sampling interval.
  47   // Note that this is a system-wide setting.
  48   static bool SetSamplingInterval(base::TimeDelta sampling_interval);
  49   static bool GetSamplingInterval(base::TimeDelta* sampling_interval);
  50
  51   // Accessors.
  52   bool is_started() const { return is_started_; }
  53
  54   // It is safe to read the counts in the sampling buckets at any time.
  55   // Note however that there's no guarantee that you'll read consistent counts
  56   // until the profiler has been stopped, as the counts may be updating on other
  57   // CPU cores.
  58   const std::vector<ULONG>& buckets() const { return buckets_; }
  59
  60  private:
  61   // Handle to the corresponding kernel object.
  62   ScopedHandle profile_handle_;
  63   // True iff this profiler is started.
  64   bool is_started_;
  65   std::vector<ULONG> buckets_;
  66
  67   DISALLOW_COPY_AND_ASSIGN(SamplingProfiler);
  68 };
  69
  70 }  // namespace win
  71 }  // namespace base
  72
  73 #endif  // BASE_WIN_SAMPLING_PROFILER_H_