[jira] [Comment Edited] (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 edited comment on IGNITE-15460 at 9/17/21, 4:53 AM:
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Closing the issue without a fix: discussed this with the community and there were different opinions whether 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.

I agree that the latter is a valid consideration and it requires additional discussion how to address this problem. We may decide to keep the existing warning and update the Ignite documentation instead with the advice above. In this case the documentation should also specify how to estimated required direct memory.


was (Author: kukushal):
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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