[jira] [Assigned] (IMPALA-12122) Use isb instead of yield on arm64

["Laszlo Gaal (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-12122?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Laszlo Gaal reassigned IMPALA-12122:
------------------------------------

    Assignee: Sebastian Pop

> Use isb instead of yield on arm64
> ---------------------------------
>
>                 Key: IMPALA-12122
>                 URL: https://issues.apache.org/jira/browse/IMPALA-12122
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>    Affects Versions: Impala 4.2.0
>            Reporter: Sebastian Pop
>            Assignee: Sebastian Pop
>            Priority: Major
>
> A "yield" instruction in aarch64 is essentially a nop, and does not cause enough delay to help backoff. 
> "isb" is a barrier that, especially inside a loop, creates a small delay without consuming ALU resources. 
> Experiments shown that adding the isb instruction improves stability and reduces result jitter. 
> Adding more delay than a single isb reduces performance.



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