MethodHandlesArrayElementGetterBench.testCreate Analysis. Copyright 2016, Oracle and/or its affiliates. All rights reserved.

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2 MethodHandlesArrayElementGetterBench.testCreate Analysis

3 Overview Benchmark : nom.indy.methodhandlesarrayelementgetterbench.testcreate Results with JDK8 (ops/us) JDK8 Intel 234 T8 T8 with -XX:FreqInlineSize= (Intel is 2.5x than this) 189 (Intel is 1.2x than this) -XX:FreqInlineSize=<size> : Integer specifying maximum number of bytecode instructions in a frequently executed method which gets inlined. Default value for Intel is 325 Default value for SPARC is 175 3

4 MethodHandlesArrayElementGetterBench.testCreate Benchmark source public MethodHandle testcreate() { return MethodHandles.arrayElementGetter(int[].class); } /*Call the same function with the same argument multiple times */ MethodHandle arrayelementgetter(class<?> arrayclass) throws IllegalArgumentException { return MethodHandleImpl.makeArrayElementAccessor(arrayClass, false); } 4

5 MethodHandlesArrayElementGetterBench.testCreate Benchmark source code static MethodHandle makearrayelementaccessor(class<?> arrayclass, boolean issetter) { if (arrayclass == Object[].class) return (issetter? ArrayAccessor.OBJECT_ARRAY_SETTER : ArrayAccessor.OBJECT_ARRAY_GETTER); if (!arrayclass.isarray()) throw newillegalargumentexception("not an array: "+arrayclass); MethodHandle[] cache = ArrayAccessor.TYPED_ACCESSORS.get(arrayClass); int cacheindex = (issetter? ArrayAccessor.SETTER_INDEX : ArrayAccessor.GETTER_INDEX); MethodHandle mh = cache[cacheindex]; if (mh!= null) return mh; mh = ArrayAccessor.getAccessor(arrayClass, issetter); MethodType correcttype = ArrayAccessor.correctType(arrayClass, issetter); if (mh.type()!= correcttype) { assert(mh.type().parametertype(0) == Object[].class); assert((issetter? mh.type().parametertype(2) : mh.type().returntype()) == Object.class); assert(issetter correcttype.parametertype(0).getcomponenttype() == correcttype.returntype()); // safe to view non-strictly, because element type follows from array type mh = mh.viewastype(correcttype, false); } mh = makeintrinsic(mh, (issetter? Intrinsic.ARRAY_STORE : Intrinsic.ARRAY_LOAD)); // Atomically update accessor cache. synchronized(cache) { if (cache[cacheindex] == null) { cache[cacheindex] = mh; } else { // Throw away newly constructed accessor and use cached version. mh = cache[cacheindex]; } } } return mh; b25/java/lang/invoke/methodhandleimpl.java#methodhandleimpl.makearrayelementaccessor%28java.lang.class%2cboolean%29 5

6 Intel disassembly (JDK8) Inline optimization Before inline optimization 6

7 T8 disassembly (JDK8) After forcing Inline optimization Does not do inline optimization, invokes call and ret. The method being called is the hotspot and not optimized. It has redundant branch instructions. 7

8 Analysis Inline method provides more opportunity to optimize. Inline method saves call, ret and stack allocate, also uses less branches -XX:FreqInlineSize controls maximum inline function size, default value for x86 is 325, for SPARC is 175. The hotspot method in this case is 285 bytes, so x86 used inline optimization, SPARC did not Adding -XX:FreqInlineSize=325 on T8 doubled the performance

9 SPARC -XX:FreqInlineSize=325 VS XX:FreqInlineSize=175 Run on java 1.8.0_77 -XX:FreqInlineSize=325 # of benchmark Percentage Improvement Performance gain >= % Performance gain > 10% % Performance loss % Performance loss >10% % All Benchmark Performance Gain Chart Performance gain Grand Total 1173 # of benchmark

10 Intel -XX:FreqInlineSize=175 VS XX:FreqInlineSize=325 Run on java 1.8.0_77 -XX:FreqInlineSize=325 # of benchmark Percentage Performance gain >= % Performance gain > 10% % Performance loss % Performance loss >10% % All Benchmark Performance Gain Chart Performance gain # of benchmark Grand Total 1173

11 Performance Gain for Each Benchmark on SPARC X axis: benchmark ID Y axis: performance gain Performance Gain for Each Benchmark on x86

12 Comparison Analysis X86: With -XX:FreqInlineSize=325, 62.6% of benchmarks performance improved, 37.4% of benchmarks lose performance SPARC: With-XX:FreqInlineSize=325, 73.2% of benchmarks performance improved on SPARC, 26.7% of benchmarks lose performance

13 Conclusion Should -XX:FreqInlineSize=325 be made default JVM configuration for SPARC?