Changeset 121511 in webkit for trunk/Source/JavaScriptCore/bytecode/ExecutionCounter.cpp

Timestamp:

Jun 28, 2012, 7:40:14 PM (13 years ago)

Author:

[email protected]

Message:

DFG recompilation heuristics should be based on count, not rate
​https://bugs.webkit.org/show_bug.cgi?id=90146

Reviewed by Oliver Hunt.

This removes a bunch of code that was previously trying to prevent spurious
reoptimizations if a large enough majority of executions of a code block did
not result in OSR exit. It turns out that this code was purely harmful. This
patch removes all of that logic and replaces it with a dead-simple
heuristic: if you exit more than N times (where N is an exponential function
of the number of times the code block has already been recompiled) then we
will recompile.

This appears to be a broad ~1% win on many benchmarks large and small.

• bytecode/CodeBlock.cpp:

(JSC::CodeBlock::CodeBlock):

• bytecode/CodeBlock.h:

(JSC::CodeBlock::osrExitCounter):
(JSC::CodeBlock::countOSRExit):
(CodeBlock):
(JSC::CodeBlock::addressOfOSRExitCounter):
(JSC::CodeBlock::offsetOfOSRExitCounter):
(JSC::CodeBlock::adjustedExitCountThreshold):
(JSC::CodeBlock::exitCountThresholdForReoptimization):
(JSC::CodeBlock::exitCountThresholdForReoptimizationFromLoop):
(JSC::CodeBlock::shouldReoptimizeNow):
(JSC::CodeBlock::shouldReoptimizeFromLoopNow):

• bytecode/ExecutionCounter.cpp:

(JSC::ExecutionCounter::setThreshold):

• bytecode/ExecutionCounter.h:

(ExecutionCounter):
(JSC::ExecutionCounter::clippedThreshold):

• dfg/DFGJITCompiler.cpp:

(JSC::DFG::JITCompiler::compileBody):

• dfg/DFGOSRExit.cpp:

(JSC::DFG::OSRExit::considerAddingAsFrequentExitSiteSlow):

• dfg/DFGOSRExitCompiler.cpp:

(JSC::DFG::OSRExitCompiler::handleExitCounts):

• dfg/DFGOperations.cpp:
• jit/JITStubs.cpp:

(JSC::DEFINE_STUB_FUNCTION):

• runtime/Options.cpp:

(Options):
(JSC::Options::initializeOptions):

• runtime/Options.h:

(Options):

File:

• trunk/Source/JavaScriptCore/bytecode/ExecutionCounter.cpp (modified) (1 diff)

trunk/Source/JavaScriptCore/bytecode/ExecutionCounter.cpp

@@ -145 +145 @@
     }
 
-    int32_t maxThreshold;
-    if (Options::randomizeExecutionCountsBetweenCheckpoints)
-        maxThreshold = codeBlock->globalObject()->weakRandomInteger() % Options::maximumExecutionCountsBetweenCheckpoints;
-    else
-        maxThreshold = Options::maximumExecutionCountsBetweenCheckpoints;
-    if (threshold > maxThreshold)
-        threshold = maxThreshold;
+    threshold = clippedThreshold(codeBlock->globalObject(), threshold);
     
     m_counter = static_cast<int32_t>(-threshold);