Squash: Fix bugs

trunk/3rdparty/gperftools-2-fit/src/sampler.cc

@@ -0,0 +1,134 @@
+// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
+// 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
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// 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 <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 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 2^58.");
+#endif
+
+namespace tcmalloc {
+
+int Sampler::GetSamplePeriod() {
+  return FLAGS_tcmalloc_sample_parameter;
+}
+
+// Run this before using your sampler
+void Sampler::Init(uint64_t seed) {
+  ASSERT(seed != 0);
+
+  // Initialize PRNG
+  rnd_ = seed;
+  // Step it forward 20 times for good measure
+  for (int i = 0; i < 20; i++) {
+    rnd_ = NextRandom(rnd_);
+  }
+  // Initialize counter
+  bytes_until_sample_ = PickNextSamplingPoint();
+}
+
+#define MAX_SSIZE (static_cast<ssize_t>(static_cast<size_t>(static_cast<ssize_t>(-1)) >> 1))
+
+// Generates a geometric variable with the specified mean (512K by default).
+// This is done by generating a random number between 0 and 1 and applying
+// the inverse cumulative distribution function for an exponential.
+// Specifically: Let m be the inverse of the sample period, then
+// the probability distribution function is m*exp(-mx) so the CDF is
+// p = 1 - exp(-mx), so
+// q = 1 - p = exp(-mx)
+// log_e(q) = -mx
+// -log_e(q)/m = x
+// log_2(q) * (-log_e(2) * 1/m) = x
+// In the code, q is actually in the range 1 to 2**26, hence the -26 below
+ssize_t Sampler::PickNextSamplingPoint() {
+  if (FLAGS_tcmalloc_sample_parameter <= 0) {
+    // In this case, we don't want to sample ever, and the larger a
+    // value we put here, the longer until we hit the slow path
+    // again. However, we have to support the flag changing at
+    // runtime, so pick something reasonably large (to keep overhead
+    // low) but small enough that we'll eventually start to sample
+    // again.
+    return 16 << 20;
+  }
+
+  rnd_ = NextRandom(rnd_);
+  // Take the top 26 bits as the random number
+  // (This plus the 1<<58 sampling bound give a max possible step of
+  // 5194297183973780480 bytes.)
+  const uint64_t prng_mod_power = 48;  // Number of bits in prng
+  // The uint32_t cast is to prevent a (hard-to-reproduce) NAN
+  // under piii debug for some binaries.
+  double q = static_cast<uint32_t>(rnd_ >> (prng_mod_power - 26)) + 1.0;
+  // Put the computed p-value through the CDF of a geometric.
+  double interval =
+      (log2(q) - 26) * (-log(2.0) * FLAGS_tcmalloc_sample_parameter);
+
+  // Very large values of interval overflow ssize_t. If we happen to
+  // hit such improbable condition, we simply cheat and clamp interval
+  // to largest supported value.
+  return static_cast<ssize_t>(
+    std::min<double>(interval, static_cast<double>(MAX_SSIZE)));
+}
+
+bool Sampler::RecordAllocationSlow(size_t k) {
+  if (!initialized_) {
+    initialized_ = true;
+    Init(reinterpret_cast<uintptr_t>(this));
+    if (static_cast<size_t>(bytes_until_sample_) >= k) {
+      bytes_until_sample_ -= k;
+      return true;
+    }
+  }
+  bytes_until_sample_ = PickNextSamplingPoint();
+  return FLAGS_tcmalloc_sample_parameter <= 0;
+}
+
+}  // namespace tcmalloc