JMH 1.11

[Aleksey Shipilev]

Hi,

JMH 1.11 is released and available at Maven Central (props to Evgeny
Mandrikov, as usual). It includes a few important changes:

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 * We know that some primitive Blackhole.consume-s, notably boolean one,
may produce an unstable score on very small nanobenchmarks. When used in
a loop, this can also be visible on larger benchmarks. While this is
something that is captured by multiple forks as run-to-run variance, it
keeps getting rediscovered as performance issue. The latest re-discovery
was by Andrei Pangin as the follow-up for a StackOverflow question.

We have reconsidered the Blackhole code shape for some primitive values,
and it brought us more uniformity with little-to-none performance hits.
While our testing and Blackhole's defense-in-depth implementation shows
no functional regressions, it makes sense to keep an eye on this during
the upgrade.

Tracking:
  https://bugs.openjdk.java.net/browse/CODETOOLS-7901494

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 * Revamped the JMH Core Benchmarks suite. This helped us greatly in
testing the Blackholes this week, but it's generally useful for
validating the benchmarking environments. Try and run this on every new
environment you are using the benchmarks on, and follow up on the
problems there. Sample report:
  http://cr.openjdk.java.net/~shade/jmh/jmh-core-benchmarks-sample.txt

You can get the latest and greatest suite by building the JMH workspace
and looking at jmh-core-benchmarks/target/jmh-core-benchmarks.jar, or
pulling out the pre-built JAR from Maven Central:

http://central.maven.org/maven2/org/openjdk/jmh/jmh-core-benchmarks/1.11/jmh-core-benchmarks-1.11-full.jar

Tracking:
  https://bugs.openjdk.java.net/browse/CODETOOLS-7901502

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 * Command line options help (available via -h) was rewritten to make it
more understandable. This hopefully helps users to discover useful
features like -rf (produce a machine-readable result file) early.

Tracking:
  https://bugs.openjdk.java.net/browse/CODETOOLS-7901501

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 * Other minor UI fixes and bugfixes

Enjoy!
-Aleksey