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Date: Wed, 30 Mar 2011 15:00:07 +0000 (UTC)
From: "Nathan Roberts (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-1796) Switch NameNode to use non-fair
 locks
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    [ https://issues.apache.org/jira/browse/HDFS-1796?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13013001#comment-13013001 ] 

Nathan Roberts commented on HDFS-1796:
--------------------------------------

I'm certainly not an expert on these two locks so there may not be anything to gain from this comment. If either of these locks can be heavily contended, then it might make sense to run something which exercises this contention to make sure the change doesn't cause our latency tail to grow dramatically.

> Switch NameNode to use non-fair locks
> -------------------------------------
>
>                 Key: HDFS-1796
>                 URL: https://issues.apache.org/jira/browse/HDFS-1796
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Hairong Kuang
>         Attachments: non-fair-lock.patch
>
>
> According to JavaDoc, a non-fair lock will normally have higher throughput than a fair lock. Our experiment also shows an improved performance when using a non-fair lock. We should switch namenode to use non-fair locks.

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