On Thu, 22 Oct 2020 20:46:15 GMT, Сергей Цыпанов <github.com+10835776+stsypa...@openjdk.org> wrote:
> As discussed in https://github.com/openjdk/jdk/pull/510 there is never a > reason to explicitly instantiate any instance of `Atomic*` class with its > default value, i.e. `new AtomicInteger(0)` could be replaced with `new > AtomicInteger()` which is faster: > @State(Scope.Thread) > @OutputTimeUnit(TimeUnit.NANOSECONDS) > @BenchmarkMode(value = Mode.AverageTime) > public class AtomicBenchmark { > @Benchmark > public Object defaultValue() { > return new AtomicInteger(); > } > @Benchmark > public Object explicitValue() { > return new AtomicInteger(0); > } > } > THis benchmark demonstrates that `explicitValue()` is much slower: > Benchmark Mode Cnt Score Error Units > AtomicBenchmark.defaultValue avgt 30 4.778 ± 0.403 ns/op > AtomicBenchmark.explicitValue avgt 30 11.846 ± 0.273 ns/op > So meanwhile https://bugs.openjdk.java.net/browse/JDK-8145948 is still in > progress we could trivially replace explicit zeroing with default > constructors gaining some performance benefit with no risk. > > I've tested the changes locally, both tier1 and tier 2 are ok. > > Could one create an issue for tracking this? This pull request has now been integrated. Changeset: 3c4fc793 Author: Sergey Tsypanov <sergei.tsypa...@yandex.ru> Committer: Daniel Fuchs <dfu...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/3c4fc793 Stats: 19 lines in 17 files changed: 0 ins; 3 del; 16 mod 8255299: Drop explicit zeroing at instantiation of Atomic* objects Reviewed-by: redestad, serb, prr ------------- PR: https://git.openjdk.java.net/jdk/pull/818
