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https://issues.apache.org/jira/browse/BEAM-13073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17448217#comment-17448217
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Valentyn Tymofieiev commented on BEAM-13073:
--------------------------------------------

The --max-****s=12  is probably --max-workers=12, not sure what causes this 
bizzare flag shortening.

> Unexpected GC when using Java 11
> --------------------------------
>
>                 Key: BEAM-13073
>                 URL: https://issues.apache.org/jira/browse/BEAM-13073
>             Project: Beam
>          Issue Type: Bug
>          Components: sdk-java-harness
>            Reporter: Luis
>            Assignee: Kenneth Knowles
>            Priority: P1
>              Labels: java11, java9, performance
>             Fix For: 2.35.0
>
>         Attachments: perf_regression_java_11.png
>
>          Time Spent: 50m
>  Remaining Estimate: 0h
>
> Beam SDK has been supporting Java 11 for a while (I guess the support was 
> introduced here https://issues.apache.org/jira/browse/BEAM-2530). 
> Unfortunately, in Spotify we are still experiencing performance issues when 
> using Beam SDK 2.32, Google Dataflow and Java 11.
> Thanks to [~emilyye] and [~iht], they confirmed JVM 11 is using SerialGC, 
> while Java 8 uses ParallelGC. It sounds like ParallelGC is a good option for 
> high throughput / low latency jobs. For Java11 we'd expect to use G1GC or 
> ParallelGC.
> This SO question [1] clarifies that JVM chooses SerialGC when it treats the 
> machine as a "client". It looks like the Java SDK container could benefit 
> from using `-XX:+AlwaysActAsServerClassMachine`. Is that correct?
> Let me know if the ticket needs further context or adjustment. (It is my 
> first time creating a ticket here).
>  [1] 
> [https://stackoverflow.com/questions/52474162/why-is-serialgc-chosen-over-g1gc]



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