Merge google-perftools r109 (the current contents of third_party/tcmalloc/vendor)

third_party/tcmalloc/chromium/src/sampler.cc

 // Copyright (c) 2008, Google Inc.
 // All rights reserved.
 // 
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 // 
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 17 matching lines @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // ---
 // All Rights Reserved.
 //
 // Author: Daniel Ford
 
 #include "sampler.h"
 
 #include <algorithm>  // For min()
-#include <cmath>
+#include <math.h>
+#include "base/commandlineflags.h"
 
 using std::min;
 
 // The approximate gap in bytes between sampling actions.
 // I.e., we take one sample approximately once every
 // tcmalloc_sample_parameter bytes of allocation
-// i.e. about once every 512KB.
+// i.e. about once every 512KB if value is 1<<19.
 #ifdef NO_TCMALLOC_SAMPLES
 DEFINE_int64(tcmalloc_sample_parameter, 0,
              "Unused: code is compiled with NO_TCMALLOC_SAMPLES");
 #else
 DEFINE_int64(tcmalloc_sample_parameter,
              EnvToInt64("TCMALLOC_SAMPLE_PARAMETER", 0),
              "The approximate gap in bytes between sampling actions. "
-             "This must be between 1 and 1<<58.");
-// Note: there are other places in this file where the number 19 occurs.
+             "This must be between 1 and 2^58.");
 #endif
 
 namespace tcmalloc {
 
 // Statics for Sampler
 double Sampler::log_table_[1<<kFastlogNumBits];
 
 // Populate the lookup table for FastLog2.
 // This approximates the log2 curve with a step function.
 // Steps have height equal to log2 of the mid-point of the step.
@@ skipping 56 matching lines @@
   // For faster performance (save ~1/20th exec time), replace
   // min(0.0, FastLog2(q) - 26)  by  (Fastlog2(q) - 26.000705)
   // The value 26.000705 is used rather than 26 to compensate
   // for inaccuracies in FastLog2 which otherwise result in a
   // negative answer.
   return static_cast<size_t>(min(0.0, (FastLog2(q) - 26)) * (-log(2.0)
                              * FLAGS_tcmalloc_sample_parameter) + 1);
 }
 
 }  // namespace tcmalloc