On Mon, 30 Aug 2021 14:26:56 GMT, Сергей Цыпанов <github.com+10835776+stsypa...@openjdk.org> wrote:
> Just a very tiny clean-up. > > There are some places in JDK code base where we call > `Enum.class.getEnumConstants()` to get all the values of the referenced > `enum`. This is excessive, less-readable and slower than just calling > `Enum.values()` as in `getEnumConstants()` we have volatile access: > > public T[] getEnumConstants() { > T[] values = getEnumConstantsShared(); > return (values != null) ? values.clone() : null; > } > > private transient volatile T[] enumConstants; > > T[] getEnumConstantsShared() { > T[] constants = enumConstants; > if (constants == null) { /* ... */ } > return constants; > } > > Calling values() method is slightly faster: > > @BenchmarkMode(Mode.AverageTime) > @OutputTimeUnit(TimeUnit.NANOSECONDS) > @Fork(jvmArgsAppend = {"-Xms2g", "-Xmx2g"}) > public class EnumBenchmark { > > @Benchmark > public Enum[] values() { > return Enum.values(); > } > > @Benchmark > public Enum[] getEnumConstants() { > return Enum.class.getEnumConstants(); > } > > private enum Enum { > A, > B > } > } > > > Benchmark Mode Cnt > Score Error Units > EnumBenchmark.getEnumConstants avgt 15 > 6,265 ± 0,051 ns/op > EnumBenchmark.getEnumConstants:·gc.alloc.rate avgt 15 > 2434,075 ± 19,568 MB/sec > EnumBenchmark.getEnumConstants:·gc.alloc.rate.norm avgt 15 > 24,002 ± 0,001 B/op > EnumBenchmark.getEnumConstants:·gc.churn.G1_Eden_Space avgt 15 > 2433,709 ± 70,216 MB/sec > EnumBenchmark.getEnumConstants:·gc.churn.G1_Eden_Space.norm avgt 15 > 23,998 ± 0,659 B/op > EnumBenchmark.getEnumConstants:·gc.churn.G1_Survivor_Space avgt 15 > 0,009 ± 0,003 MB/sec > EnumBenchmark.getEnumConstants:·gc.churn.G1_Survivor_Space.norm avgt 15 > ≈ 10⁻⁴ B/op > EnumBenchmark.getEnumConstants:·gc.count avgt 15 > 210,000 counts > EnumBenchmark.getEnumConstants:·gc.time avgt 15 > 119,000 ms > > EnumBenchmark.values avgt 15 > 4,164 ± 0,134 ns/op > EnumBenchmark.values:·gc.alloc.rate avgt 15 > 3665,341 ± 120,721 MB/sec > EnumBenchmark.values:·gc.alloc.rate.norm avgt 15 > 24,002 ± 0,001 B/op > EnumBenchmark.values:·gc.churn.G1_Eden_Space avgt 15 > 3660,512 ± 137,250 MB/sec > EnumBenchmark.values:·gc.churn.G1_Eden_Space.norm avgt 15 > 23,972 ± 0,529 B/op > EnumBenchmark.values:·gc.churn.G1_Survivor_Space avgt 15 > 0,017 ± 0,003 MB/sec > EnumBenchmark.values:·gc.churn.G1_Survivor_Space.norm avgt 15 > ≈ 10⁻⁴ B/op > EnumBenchmark.values:·gc.count avgt 15 > 262,000 counts > EnumBenchmark.values:·gc.time avgt 15 > 155,000 ms This pull request has now been integrated. Changeset: 152e6692 Author: Sergey Tsypanov <sergei.tsypa...@yandex.ru> Committer: Thomas Schatzl <tscha...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/152e66923dc36cfd83cdfe18e96631abc06b9199 Stats: 13 lines in 4 files changed: 0 ins; 2 del; 11 mod 8273140: Replace usages of Enum.class.getEnumConstants() with Enum.values() where possible Reviewed-by: tschatzl ------------- PR: https://git.openjdk.java.net/jdk/pull/5303