Integrated: 8255299: Drop explicit zeroing at instantiation of Atomic* objects
Сергей Цыпанов
github.com+10835776+stsypanov at openjdk.java.net
Wed Oct 28 12:14:48 UTC 2020
On Thu, 22 Oct 2020 20:46:15 GMT, Сергей Цыпанов <github.com+10835776+stsypanov at 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.tsypanov at yandex.ru>
Committer: Daniel Fuchs <dfuchs at 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
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