[jira] [Commented] (IGNITE-15460) Incorrect "Set max direct memory size" suggestion

["Alexey Kukushkin (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IGNITE-15460?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17416450#comment-17416450 ] 

Alexey Kukushkin commented on IGNITE-15460:
-------------------------------------------

Closing the issue without a fix: discussed the issues with the community and there were different opinions where this should be fixed. Some agree with removing the suggestion but others think it is a good practice to always specify {{MaxDirectMemorySize}}, as well as max heap size ({{-Xmx}}) and off-heap size (sum of {{DataRegionConfiguration.maxSize}}) to make it explicit that the total Ignite JVM memory does not exceed physical RAM that could be allocated to the JVM process.

> Incorrect "Set max direct memory size" suggestion
> -------------------------------------------------
>
>                 Key: IGNITE-15460
>                 URL: https://issues.apache.org/jira/browse/IGNITE-15460
>             Project: Ignite
>          Issue Type: Improvement
>    Affects Versions: 2.10
>            Reporter: Alexey Kukushkin
>            Priority: Major
>
> Ignite always outputs this performance suggestion on startup:
> {{Set max direct memory size if getting 'OOME: Direct buffer memory' (add '-XX:MaxDirectMemorySize=<size>[g|G|m|M|k|K]' to JVM options)}}
>  
> That is incorrect since:
>  * The Ignite [Memory and JVM Tuning|https://ignite.apache.org/docs/latest/perf-and-troubleshooting/memory-tuning#memory-and-jvm-tuning] page suggests NOT to explicitly set the {{MaxDirectMemorySize}} (unless native persistence is used but in this case set it to {{walSegmentSize * 4}}). Not setting {{MaxDirectMemorySize}} seems the right default option since in this case JVM would choose the most appropriate default size.
>  * Increasing direct memory size when getting OOME for direct memory seems too obvious to always print this information.



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