[jira] [Commented] (HDDS-2342) ContainerStateMachine$chunkExecutor threads hold onto native memory

["mingchao zhao (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDDS-2342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17650537#comment-17650537 ] 

mingchao zhao commented on HDDS-2342:
-------------------------------------

Ozone 1.3.0 had been released and we currently have more than 600 open issues targeted for 1.3.0. I am moving the target field to 1.4.0.

If there is anything needs to be discussed about the Target Version, Please reach out to me via Apache email or Slack.

> ContainerStateMachine$chunkExecutor threads hold onto native memory
> -------------------------------------------------------------------
>
>                 Key: HDDS-2342
>                 URL: https://issues.apache.org/jira/browse/HDDS-2342
>             Project: Apache Ozone
>          Issue Type: Bug
>          Components: Ozone Datanode
>            Reporter: Lokesh Jain
>            Assignee: Lokesh Jain
>            Priority: Major
>              Labels: TriagePending
>
> In a heap dump many threads in ContainerStateMachine$chunkExecutor holds onto native memory in the ThreadLocal map. Every such thread holds onto chunk worth of DirectByteBuffer. Since these threads are involved in write and read chunk operations, the JVM allocates chunk (16MB) worth of DirectByteBuffer in the ThreadLocalMap for every thread involved in IO. Also the native memory would not be GC'ed as long as the thread is alive.
> It would be better to reduce the default number of chunk executor threads and have them in proportion to number of disks on the datanode. We should also use DirectByeBuffers for the IO on datanode. Currently we allocate HeapByteBuffer which needs to be backed by DirectByteBuffer. If we can use a DirectByteBuffer we can avoid a buffer copy.



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