RFR: 8308479: [s390x] Implement alternative fast-locking scheme [v7]

[Martin Doerr]

On Mon, 19 Jun 2023 08:23:40 GMT, Amit Kumar <amitkumar at openjdk.org> wrote:

>> This PR implements new fast-locking scheme for s390x. Additionally few parameters have been renamed to be in sync with PPC.
>> 
>> Testing done (for release, fastdebug and slowdebug build):
>> All `test/jdk/java/util/concurrent` test with parameters:
>> * LockingMode=2 
>> * LockingMode=2 with -Xint
>> * LockingMode=2 with -XX:TieredStopAtLevel=1
>> * LockingMode=2 with -XX:-TieredCompilation
>> 
>> Result is consistently similar to Aarch(MacOS) and PPC, All of 124 tests are passing except `MapLoops.java` because in the 2nd part for this testcase, jvm starts with `HeavyMonitors` which conflict with `LockingMode=2`
>> 
>> BenchMark Result for Renaissance-jmh:
>> 
>> | Benchmark                                | Without fastLock (ms/op) | With fastLock (ms/op) | Improvement |
>> |------------------------------------------|-------------------------|----------------------|-------------|
>> | o.r.actors.JmhAkkaUct.runOperation        | 1565.080                | 1365.877             | 12.70%      |
>> | o.r.actors.JmhReactors.runOperation       | 9316.972                | 10592.982            | -13.70%     |
>> | o.r.jdk.concurrent.JmhFjKmeans.runOperation | 1257.183                | 1235.530             | 1.73%       |
>> | o.r.jdk.concurrent.JmhFutureGenetic.runOperation | 1925.158                | 2073.066             | -7.69%      |
>> | o.r.jdk.streams.JmhParMnemonics.runOperation | 2746.664                | 2836.085             | -3.24%      |
>> | o.r.jdk.streams.JmhScrabble.runOperation   | 76.774                  | 74.239               | 3.31%       |
>> | o.r.rx.JmhRxScrabble.runOperation          | 162.270                 | 167.061              | -2.96%      |
>> | o.r.scala.sat.JmhScalaDoku.runOperation    | 3333.711                | 3271.078             | 1.88%       |
>> | o.r.scala.stdlib.JmhScalaKmeans.runOperation | 182.746                 | 182.153              | 0.33%       |
>> | o.r.scala.stm.JmhPhilosophers.runOperation | 15003.329               | 13396.921            | 10.57%      |
>> | o.r.scala.stm.JmhScalaStmBench7.runOperation | 1669.090                | 1579.900             | 5.34%       |
>> | o.r.twitter.finagle.JmhFinagleChirper.runOperation | 9601.963                | 10034.404            | -4.52%      |
>> | o.r.twitter.finagle.JmhFinagleHttp.runOperation | 4403.725                | 4746.707             | -7.79%      |
>> 
>> 
>> DaCapo Benchmark Result:
>> 
>> | Benchmark                | Without fast lock (msec) | With fast lock (msec) | Improvement |
>> |--...
>
> Amit Kumar has updated the pull request incrementally with one additional commit since the last revision:
> 
>   minor comment update

Are the benchmark results stable or do they have a large variance?
Did you also compare against the version without your changes? That should be done for sanity checking. You have modified the code for the legacy mode, too.
I'm not sure what you mean by "With/Without fastLock"? Patch applied? LockingMode selection?

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PR Comment: https://git.openjdk.org/jdk/pull/14414#issuecomment-1603263116