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

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.h (modified) (2 diffs)

trunk/Source/JavaScriptCore/bytecode/ExecutionCounter.h

@@ -27 +27 @@
 #define ExecutionCounter_h
 
+#include "JSGlobalObject.h"
+#include "Options.h"
 #include <wtf/SimpleStats.h>
 
@@ -43 +45 @@
     static double applyMemoryUsageHeuristics(int32_t value, CodeBlock*);
     static int32_t applyMemoryUsageHeuristicsAndConvertToInt(int32_t value, CodeBlock*);
+    template<typename T>
+    static T clippedThreshold(JSGlobalObject* globalObject, T threshold)
+    {
+        int32_t maxThreshold;
+        if (Options::randomizeExecutionCountsBetweenCheckpoints)
+            maxThreshold = globalObject->weakRandomInteger() % Options::maximumExecutionCountsBetweenCheckpoints;
+        else
+            maxThreshold = Options::maximumExecutionCountsBetweenCheckpoints;
+        if (threshold > maxThreshold)
+            threshold = maxThreshold;
+        return threshold;
+    }
 
     static int32_t formattedTotalCount(float value)