On Fri, 7 Jul 2023 08:29:06 GMT, Hamlin Li <m...@openjdk.org> wrote: >> The below benchmark files have scaling issues due to cache contention and >> leads to poor scaling when run on multiple threads. The patch sets the scope >> from benchmark level to thread level to fix the issue: >> - org/openjdk/bench/java/io/DataOutputStreamTest.java >> - org/openjdk/bench/java/lang/ArrayCopyObject.java >> - org/openjdk/bench/java/lang/ArrayFiddle.java >> - org/openjdk/bench/java/time/format/DateTimeFormatterBench.java >> - org/openjdk/bench/jdk/incubator/vector/IndexInRangeBenchmark.java >> - org/openjdk/bench/jdk/incubator/vector/MemorySegmentVectorAccess.java >> - org/openjdk/bench/jdk/incubator/vector/StoreMaskedBenchmark.java >> - org/openjdk/bench/jdk/incubator/vector/StoreMaskedIOOBEBenchmark.java >> - org/openjdk/bench/vm/compiler/ArrayFill.java >> - org/openjdk/bench/vm/compiler/IndexVector.java >> >> Also removing the static scope for variables in >> org/openjdk/bench/jdk/incubator/vector/VectorFPtoIntCastOperations.java for >> better scaling. >> >> Please review and share your feedback. >> >> Thanks, >> Swati > > Hi, > I'm not sure if I understand this improvement correctly. > I'm not quite familiar with JMH and it's annotations, but seems to me, the > change from `@State(Scope.Benchmark)` to `@State(Scope.Thread)` should not > improve the performance by reducing cache contention, as in the jmh doc it > says "State objects are usually injected into Benchmark methods as > ***arguments***, and JMH takes care of their instantiation and sharing.", > this seems mean that @State only matters when the annotated class is used as > a parameter of a @Benchmark method, but in the tests you modifed, seems there > is no such use case. > Please also check the sample usages at > https://github.com/openjdk/jmh/blob/master/jmh-samples/src/main/java/org/openjdk/jmh/samples/JMHSample_03_States.java.
@Hamlin-Li The PR is fully correct. Don't forget, every Java instance method has a specific argument which called "this". That is why @State annotation is working. ------------- PR Comment: https://git.openjdk.org/jdk/pull/14746#issuecomment-1625627033
