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/*
* Copyright (C) 2012, 2013 Apple 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:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 APPLE INC. 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.
*/
#ifndef CodeCache_h
#define CodeCache_h
#include "CodeSpecializationKind.h"
#include "ParserModes.h"
#include "SourceCode.h"
#include "SourceCodeKey.h"
#include "Strong.h"
#include "VariableEnvironment.h"
#include <wtf/CurrentTime.h>
#include <wtf/Forward.h>
#include <wtf/RandomNumber.h>
#include <wtf/WeakRandom.h>
#include <wtf/text/WTFString.h>
namespace JSC {
class EvalExecutable;
class FunctionMetadataNode;
class Identifier;
class JSScope;
class ParserError;
class ProgramExecutable;
class ModuleProgramExecutable;
class UnlinkedCodeBlock;
class UnlinkedEvalCodeBlock;
class UnlinkedModuleProgramCodeBlock;
class UnlinkedFunctionCodeBlock;
class UnlinkedFunctionExecutable;
class UnlinkedProgramCodeBlock;
class VM;
class SourceCode;
class SourceProvider;
struct SourceCodeValue {
SourceCodeValue()
{
}
SourceCodeValue(VM& vm, JSCell* cell, int64_t age)
: cell(vm, cell)
, age(age)
{
}
Strong<JSCell> cell;
int64_t age;
};
class CodeCacheMap {
public:
typedef HashMap<SourceCodeKey, SourceCodeValue, SourceCodeKeyHash, SourceCodeKeyHashTraits> MapType;
typedef MapType::iterator iterator;
typedef MapType::AddResult AddResult;
CodeCacheMap()
: m_size(0)
, m_sizeAtLastPrune(0)
, m_timeAtLastPrune(monotonicallyIncreasingTime())
, m_minCapacity(0)
, m_capacity(0)
, m_age(0)
{
}
SourceCodeValue* findCacheAndUpdateAge(const SourceCodeKey& key)
{
prune();
iterator findResult = m_map.find(key);
if (findResult == m_map.end())
return nullptr;
int64_t age = m_age - findResult->value.age;
if (age > m_capacity) {
// A requested object is older than the cache's capacity. We can
// infer that requested objects are subject to high eviction probability,
// so we grow the cache to improve our hit rate.
m_capacity += recencyBias * oldObjectSamplingMultiplier * key.length();
} else if (age < m_capacity / 2) {
// A requested object is much younger than the cache's capacity. We can
// infer that requested objects are subject to low eviction probability,
// so we shrink the cache to save memory.
m_capacity -= recencyBias * key.length();
if (m_capacity < m_minCapacity)
m_capacity = m_minCapacity;
}
findResult->value.age = m_age;
m_age += key.length();
return &findResult->value;
}
AddResult addCache(const SourceCodeKey& key, const SourceCodeValue& value)
{
prune();
AddResult addResult = m_map.add(key, value);
ASSERT(addResult.isNewEntry);
m_size += key.length();
m_age += key.length();
return addResult;
}
void remove(iterator it)
{
m_size -= it->key.length();
m_map.remove(it);
}
void clear()
{
m_size = 0;
m_age = 0;
m_map.clear();
}
int64_t age() { return m_age; }
private:
// This constant factor biases cache capacity toward allowing a minimum
// working set to enter the cache before it starts evicting.
static const double workingSetTime;
static const int64_t workingSetMaxBytes = 16000000;
static const size_t workingSetMaxEntries = 2000;
// This constant factor biases cache capacity toward recent activity. We
// want to adapt to changing workloads.
static const int64_t recencyBias = 4;
// This constant factor treats a sampled event for one old object as if it
// happened for many old objects. Most old objects are evicted before we can
// sample them, so we need to extrapolate from the ones we do sample.
static const int64_t oldObjectSamplingMultiplier = 32;
size_t numberOfEntries() const { return static_cast<size_t>(m_map.size()); }
bool canPruneQuickly() const { return numberOfEntries() < workingSetMaxEntries; }
void pruneSlowCase();
void prune()
{
if (m_size <= m_capacity && canPruneQuickly())
return;
if (monotonicallyIncreasingTime() - m_timeAtLastPrune < workingSetTime
&& m_size - m_sizeAtLastPrune < workingSetMaxBytes
&& canPruneQuickly())
return;
pruneSlowCase();
}
MapType m_map;
int64_t m_size;
int64_t m_sizeAtLastPrune;
double m_timeAtLastPrune;
int64_t m_minCapacity;
int64_t m_capacity;
int64_t m_age;
};
// Caches top-level code such as <script>, eval(), new Function, and JSEvaluateScript().
class CodeCache {
WTF_MAKE_FAST_ALLOCATED;
public:
CodeCache();
~CodeCache();
UnlinkedProgramCodeBlock* getProgramCodeBlock(VM&, ProgramExecutable*, const SourceCode&, JSParserBuiltinMode, JSParserStrictMode, DebuggerMode, ProfilerMode, ParserError&);
UnlinkedEvalCodeBlock* getEvalCodeBlock(VM&, EvalExecutable*, const SourceCode&, JSParserBuiltinMode, JSParserStrictMode, ThisTDZMode, bool, DebuggerMode, ProfilerMode, ParserError&, const VariableEnvironment*);
UnlinkedModuleProgramCodeBlock* getModuleProgramCodeBlock(VM&, ModuleProgramExecutable*, const SourceCode&, JSParserBuiltinMode, DebuggerMode, ProfilerMode, ParserError&);
UnlinkedFunctionExecutable* getFunctionExecutableFromGlobalCode(VM&, const Identifier&, const SourceCode&, ParserError&);
void clear()
{
m_sourceCode.clear();
}
private:
template <class UnlinkedCodeBlockType, class ExecutableType>
UnlinkedCodeBlockType* getGlobalCodeBlock(VM&, ExecutableType*, const SourceCode&, JSParserBuiltinMode, JSParserStrictMode, ThisTDZMode, bool, DebuggerMode, ProfilerMode, ParserError&, const VariableEnvironment*);
CodeCacheMap m_sourceCode;
};
}
#endif // CodeCache_h
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