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From: "Haohui Mai (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HDFS-8900) Compact XAttrs to optimize memory
 footprint.
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    [ https://issues.apache.org/jira/browse/HDFS-8900?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14715502#comment-14715502 ] 

Haohui Mai commented on HDFS-8900:
----------------------------------

bq. The findbugs doesn't exist. (The existing findbugs were in pre-patch).

It appears that this jira introduces two new findbugs warnings in Jenkins.

https://builds.apache.org/job/PreCommit-HDFS-Build/12120/artifact/patchprocess/trunkFindbugsWarningshadoop-hdfs.html



> Compact XAttrs to optimize memory footprint.
> --------------------------------------------
>
>                 Key: HDFS-8900
>                 URL: https://issues.apache.org/jira/browse/HDFS-8900
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>            Reporter: Yi Liu
>            Assignee: Yi Liu
>             Fix For: 2.8.0
>
>         Attachments: HDFS-8900.001.patch, HDFS-8900.002.patch, HDFS-8900.003.patch, HDFS-8900.004.patch, HDFS-8900.005.patch
>
>
> {code}
> private final ImmutableList<XAttr> xAttrs;
> {code}
> Currently we use above in XAttrFeature, it's not efficient from memory point of view, since {{ImmutableList}} and {{XAttr}} have object memory overhead, and each object has memory alignment. 
> We can use a {{byte[]}} in XAttrFeature and do some compact in {{XAttr}}.



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