On Mon, 3 Jun 2024 18:00:35 GMT, Sean Gwizdak <d...@openjdk.org> wrote:
>> Improve the speed of Method.hashCode by caching the hashcode on first use. >> I've seen an application where Method.hashCode is a hot path, and this is a >> fairly simple speedup. The memory overhead is low. >> >> This addresses issue >> [JDK-8332249](https://bugs.openjdk.org/browse/JDK-8332249). >> >> Before: >> >> Benchmark Mode Cnt Score Error Units >> # Intel Skylake >> MethodHashCode.benchmarkHashCode avgt 5 1.843 ± 0.149 ns/op >> # Arm Neoverse N1 >> MethodHashCode.benchmarkHashCode avgt 5 2.363 ± 0.091 ns/op >> >> >> >> After: >> >> >> Benchmark Mode Cnt Score Error Units >> # Intel Skylake >> MethodHashCode.benchmarkHashCode avgt 5 1.121 ± 1.189 ns/op >> # Arm Neoverse N1 >> MethodHashCode.benchmarkHashCode avgt 5 1.001 ± 0.001 ns/op > > Sean Gwizdak has updated the pull request with a new target base due to a > merge or a rebase. The incremental webrev excludes the unrelated changes > brought in by the merge/rebase. The pull request contains six additional > commits since the last revision: > > - Remove trailing whitespace. > - Move hashCode benchmark into the newly created MethodBenchmark file > - Merge branch 'master' into method-hashcode-JDK-8332249 > - Remove changes to JavaDoc per guidance. > - Fix whitespace issues pointed by the bot > - Micro-optimize Method.hashCode As usual in these cases, we need to make a footprint argument as well. `Method` is a special class with lots of injected fields, so the only "true" source of layout information is `-XX:+PrintFieldLayout`. It tells me there is a 4-byte tail due to object alignment in compressed oops mode. This can accommodate a new `int` field. There seems to be no space when compressed oops are disabled. # Out of the box, compressed oops enabled Layout of class java/lang/reflect/Method Instance fields: @0 12/- RESERVED @12 "override" Z 1/1 INHERITED @13 "callerSensitive" B 1/1 REGULAR @14 2/1 EMPTY @16 "accessCheckCache" Ljava/lang/Object; 4/4 INHERITED @20 "parameterData" Ljava/lang/reflect/Executable$ParameterData; 4/4 INHERITED @24 "declaredAnnotations" Ljava/util/Map; 4/4 INHERITED @28 "slot" I 4/4 REGULAR @32 "modifiers" I 4/4 REGULAR @36 "clazz" Ljava/lang/Class; 4/4 REGULAR @40 "name" Ljava/lang/String; 4/4 REGULAR @44 "returnType" Ljava/lang/Class; 4/4 REGULAR @48 "parameterTypes" [Ljava/lang/Class; 4/4 REGULAR @52 "exceptionTypes" [Ljava/lang/Class; 4/4 REGULAR @56 "signature" Ljava/lang/String; 4/4 REGULAR @60 "genericInfo" Lsun/reflect/generics/repository/MethodRepository; 4/4 REGULAR @64 "annotations" [B 4/4 REGULAR @68 "parameterAnnotations" [B 4/4 REGULAR @72 "annotationDefault" [B 4/4 REGULAR @76 "methodAccessor" Ljdk/internal/reflect/MethodAccessor; 4/4 REGULAR @80 "root" Ljava/lang/reflect/Method; 4/4 REGULAR Instance size = 88 bytes # -XX:-UseCompressedOops Layout of class java/lang/reflect/Method Instance fields: @0 12/- RESERVED @12 "override" Z 1/1 INHERITED @13 "callerSensitive" B 1/1 REGULAR @14 2/1 EMPTY @16 "accessCheckCache" Ljava/lang/Object; 8/8 INHERITED @24 "parameterData" Ljava/lang/reflect/Executable$ParameterData; 8/8 INHERITED @32 "declaredAnnotations" Ljava/util/Map; 8/8 INHERITED @40 "slot" I 4/4 REGULAR @44 "modifiers" I 4/4 REGULAR @48 "clazz" Ljava/lang/Class; 8/8 REGULAR @56 "name" Ljava/lang/String; 8/8 REGULAR @64 "returnType" Ljava/lang/Class; 8/8 REGULAR @72 "parameterTypes" [Ljava/lang/Class; 8/8 REGULAR @80 "exceptionTypes" [Ljava/lang/Class; 8/8 REGULAR @88 "signature" Ljava/lang/String; 8/8 REGULAR @96 "genericInfo" Lsun/reflect/generics/repository/MethodRepository; 8/8 REGULAR @104 "annotations" [B 8/8 REGULAR @112 "parameterAnnotations" [B 8/8 REGULAR @120 "annotationDefault" [B 8/8 REGULAR @128 "methodAccessor" Ljdk/internal/reflect/MethodAccessor; 8/8 REGULAR @136 "root" Ljava/lang/reflect/Method; 8/8 REGULAR Instance size = 144 bytes ------------- PR Comment: https://git.openjdk.org/jdk/pull/19433#issuecomment-2160170846
