Changeset 99375 in webkit

Timestamp:

Nov 6, 2011, 3:54:59 AM (15 years ago)

Author:

fpizlo@apple.com

Message:

Value profiling should just use two buckets
​https://bugs.webkit.org/show_bug.cgi?id=71619

Reviewed by Gavin Barraclough.

Added one more configuration options (like Heuristics::minimumOptimizationDelay),
improved debugging in JIT optimization support, changed the number of buckets
in the value profile from 9 to 2, and wrote a more optimal value profiling path
in the old JIT to take advantage of this. It's still possible to play around with
larger numbers of buckets, and we should probably keep this for a little while
until we convince ourselves that using just two buckets is the right call.

• bytecode/CodeBlock.cpp:

(JSC::CodeBlock::shouldOptimizeNow):

• bytecode/ValueProfile.h:
• jit/JITInlineMethods.h:

(JSC::JIT::emitValueProfilingSite):

• jit/JITStubs.cpp:

(JSC::DEFINE_STUB_FUNCTION):

• runtime/Heuristics.cpp:

(JSC::Heuristics::initializeHeuristics):

• runtime/Heuristics.h:

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• bytecode/CodeBlock.cpp (modified) (1 diff)
• bytecode/ValueProfile.h (modified) (1 diff)
• jit/JITInlineMethods.h (modified) (3 diffs)
• jit/JITStubs.cpp (modified) (3 diffs)
• runtime/Heuristics.cpp (modified) (2 diffs)
• runtime/Heuristics.h (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2011-11-05  Filip Pizlo  <fpizlo@apple.com>
+
+        Value profiling should just use two buckets
+        https://bugs.webkit.org/show_bug.cgi?id=71619
+
+        Reviewed by Gavin Barraclough.
+        
+        Added one more configuration options (like Heuristics::minimumOptimizationDelay),
+        improved debugging in JIT optimization support, changed the number of buckets
+        in the value profile from 9 to 2, and wrote a more optimal value profiling path
+        in the old JIT to take advantage of this. It's still possible to play around with
+        larger numbers of buckets, and we should probably keep this for a little while
+        until we convince ourselves that using just two buckets is the right call.
+
+        * bytecode/CodeBlock.cpp:
+        (JSC::CodeBlock::shouldOptimizeNow):
+        * bytecode/ValueProfile.h:
+        * jit/JITInlineMethods.h:
+        (JSC::JIT::emitValueProfilingSite):
+        * jit/JITStubs.cpp:
+        (JSC::DEFINE_STUB_FUNCTION):
+        * runtime/Heuristics.cpp:
+        (JSC::Heuristics::initializeHeuristics):
+        * runtime/Heuristics.h:
+
 2011-11-03  Filip Pizlo  <fpizlo@apple.com>
 

trunk/Source/JavaScriptCore/bytecode/CodeBlock.cpp

@@ -1957 +1957 @@
 
     if ((!numberOfNonArgumentValueProfiles || (double)numberOfLiveNonArgumentValueProfiles / numberOfNonArgumentValueProfiles >= Heuristics::desiredProfileLivenessRate)
-        && (!numberOfValueProfiles() || (double)numberOfSamplesInProfiles / ValueProfile::numberOfBuckets / numberOfValueProfiles() >= Heuristics::desiredProfileFullnessRate))
+        && (!numberOfValueProfiles() || (double)numberOfSamplesInProfiles / ValueProfile::numberOfBuckets / numberOfValueProfiles() >= Heuristics::desiredProfileFullnessRate)
+        && static_cast<unsigned>(m_optimizationDelayCounter) + 1 >= Heuristics::minimumOptimizationDelay)
         return true;
     
+    ASSERT(m_optimizationDelayCounter < std::numeric_limits<uint8_t>::max());
     m_optimizationDelayCounter++;
     optimizeAfterWarmUp();

trunk/Source/JavaScriptCore/bytecode/ValueProfile.h

@@ -39 +39 @@
 #if ENABLE(VALUE_PROFILER)
 struct ValueProfile {
-    static const unsigned logNumberOfBuckets = 3; // 8 buckets
+    static const unsigned logNumberOfBuckets = 0; // 1 bucket
     static const unsigned numberOfBuckets = 1 << logNumberOfBuckets;
     static const unsigned numberOfSpecFailBuckets = 1;

trunk/Source/JavaScriptCore/jit/JITInlineMethods.h

@@ -463 +463 @@
     
     const RegisterID value = regT0;
+#if USE(JSVALUE32_64)
+    const RegisterID valueTag = regT1;
+#endif
     const RegisterID scratch = regT3;
     
@@ -475 +478 @@
     ASSERT(valueProfile);
     
+    if (ValueProfile::numberOfBuckets == 1) {
+        // We're in a simple configuration: only one bucket, so we can just do a direct
+        // store.
+#if USE(JSVALUE64)
+        storePtr(value, valueProfile->m_buckets);
+#else
+        EncodedValueDescriptor* descriptor = bitwise_cast<EncodedValueDescriptor*>(valueProfile->m_buckets);
+        store32(value, &descriptor->asBits.payload);
+        store32(valueTag, &descriptor->asBits.tag);
+#endif
+        return;
+    }
+    
     if (m_randomGenerator.getUint32() & 1)
         add32(Imm32(1), bucketCounterRegister);
@@ -484 +500 @@
     storePtr(value, BaseIndex(scratch, bucketCounterRegister, TimesEight));
 #elif USE(JSVALUE32_64)
-    const RegisterID valueTag = regT1;
     store32(value, BaseIndex(scratch, bucketCounterRegister, TimesEight, OBJECT_OFFSETOF(JSValue, u.asBits.payload)));
     store32(valueTag, BaseIndex(scratch, bucketCounterRegister, TimesEight, OBJECT_OFFSETOF(JSValue, u.asBits.tag)));

trunk/Source/JavaScriptCore/jit/JITStubs.cpp

@@ -1959 +1959 @@
     if (void* address = DFG::prepareOSREntry(callFrame, optimizedCodeBlock, bytecodeIndex)) {
 #if ENABLE(JIT_VERBOSE_OSR)
-        printf("Optimizing %p from loop succeeded, performing OSR.\n", codeBlock);
+        printf("Optimizing %p from loop succeeded, performing OSR after a delay of %u.\n", codeBlock, codeBlock->optimizationDelayCounter());
 #endif
 
@@ -1969 +1969 @@
     
 #if ENABLE(JIT_VERBOSE_OSR)
-    printf("Optimizing %p from loop succeeded, OSR failed.\n", codeBlock);
+    printf("Optimizing %p from loop succeeded, OSR failed, after a delay of %u.\n", codeBlock, codeBlock->optimizationDelayCounter());
 #endif
 
@@ -2059 +2059 @@
 
 #if ENABLE(JIT_VERBOSE_OSR)
-    printf("Optimizing %p from return succeeded.\n", codeBlock);
+    printf("Optimizing %p from return succeeded after a delay of %u.\n", codeBlock, codeBlock->optimizationDelayCounter());
 #endif
     

trunk/Source/JavaScriptCore/runtime/Heuristics.cpp

@@ -75 +75 @@
 unsigned reoptimizationRetryCounterStep;
 
+unsigned minimumOptimizationDelay;
 unsigned maximumOptimizationDelay;
 double desiredProfileLivenessRate;
@@ -158 +159 @@
     SET(reoptimizationRetryCounterStep, 1);
 
+    SET(minimumOptimizationDelay,   1);
     SET(maximumOptimizationDelay,   5);
     SET(desiredProfileLivenessRate, 0.75);

trunk/Source/JavaScriptCore/runtime/Heuristics.h

@@ -61 +61 @@
 extern unsigned reoptimizationRetryCounterStep;
 
+extern unsigned minimumOptimizationDelay;
 extern unsigned maximumOptimizationDelay;
 extern double desiredProfileLivenessRate;