bytecode/ExecutionCounter.h

   1 /*
   2  * Copyright (C) 2012, 2014 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef ExecutionCounter_h
  27 #define ExecutionCounter_h
  28
  29 #include "JSGlobalObject.h"
  30 #include "Options.h"
  31 #include <wtf/PrintStream.h>
  32 #include <wtf/SimpleStats.h>
  33
  34 namespace JSC {
  35
  36 class CodeBlock;
  37
  38 enum CountingVariant {
  39     CountingForBaseline,
  40     CountingForUpperTiers
  41 };
  42
  43 double applyMemoryUsageHeuristics(int32_t value, CodeBlock*);
  44 int32_t applyMemoryUsageHeuristicsAndConvertToInt(int32_t value, CodeBlock*);
  45
  46 inline int32_t formattedTotalExecutionCount(float value)
  47 {
  48     union {
  49         int32_t i;
  50         float f;
  51     } u;
  52     u.f = value;
  53     return u.i;
  54 }
  55
  56 template<CountingVariant countingVariant>
  57 class ExecutionCounter {
  58 public:
  59     ExecutionCounter();
  60     void forceSlowPathConcurrently(); // If you use this, checkIfThresholdCrossedAndSet() may still return false.
  61     bool checkIfThresholdCrossedAndSet(CodeBlock*);
  62     void setNewThreshold(int32_t threshold, CodeBlock*);
  63     void deferIndefinitely();
  64     double count() const { return static_cast<double>(m_totalCount) + m_counter; }
  65     void dump(PrintStream&) const;
  66
  67     static int32_t maximumExecutionCountsBetweenCheckpoints()
  68     {
  69         switch (countingVariant) {
  70         case CountingForBaseline:
  71             return Options::maximumExecutionCountsBetweenCheckpointsForBaseline();
  72         case CountingForUpperTiers:
  73             return Options::maximumExecutionCountsBetweenCheckpointsForUpperTiers();
  74         default:
  75             RELEASE_ASSERT_NOT_REACHED();
  76             return 0;
  77         }
  78     }
  79
  80     template<typename T>
  81     static T clippedThreshold(JSGlobalObject* globalObject, T threshold)
  82     {
  83         int32_t maxThreshold;
  84         if (Options::randomizeExecutionCountsBetweenCheckpoints())
  85             maxThreshold = globalObject->weakRandomInteger() % maximumExecutionCountsBetweenCheckpoints();
  86         else
  87             maxThreshold = maximumExecutionCountsBetweenCheckpoints();
  88         if (threshold > maxThreshold)
  89             threshold = maxThreshold;
  90         return threshold;
  91     }
  92
  93 private:
  94     bool hasCrossedThreshold(CodeBlock*) const;
  95     bool setThreshold(CodeBlock*);
  96     void reset();
  97
  98 public:
  99     // NB. These are intentionally public because it will be modified from machine code.
 100
 101     // This counter is incremented by the JIT or LLInt. It starts out negative and is
 102     // counted up until it becomes non-negative. At the start of a counting period,
 103     // the threshold we wish to reach is m_totalCount + m_counter, in the sense that
 104     // we will add X to m_totalCount and subtract X from m_counter.
 105     int32_t m_counter;
 106
 107     // Counts the total number of executions we have seen plus the ones we've set a
 108     // threshold for in m_counter. Because m_counter's threshold is negative, the
 109     // total number of actual executions can always be computed as m_totalCount +
 110     // m_counter.
 111     float m_totalCount;
 112
 113     // This is the threshold we were originally targetting, without any correction for
 114     // the memory usage heuristics.
 115     int32_t m_activeThreshold;
 116 };
 117
 118 typedef ExecutionCounter<CountingForBaseline> BaselineExecutionCounter;
 119 typedef ExecutionCounter<CountingForUpperTiers> UpperTierExecutionCounter;
 120
 121 } // namespace JSC
 122
 123 #endif // ExecutionCounter_h
 124