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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1148) Convert FSDataset to ReadWriteLock
Date Sat, 14 Feb 2015 02:43:12 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14321180#comment-14321180
] 

Todd Lipcon commented on HDFS-1148:
-----------------------------------

I don't think this is nearly as useful anymore now that HBase and other apps that do a large
number of random reads are usually using short-circuit read and thus avoiding any datanode
code in their hot path. If we want to optimize the remote read random read rate, this would
be useful for that purpose -- just doesn't seem urgent.

> Convert FSDataset to ReadWriteLock
> ----------------------------------
>
>                 Key: HDFS-1148
>                 URL: https://issues.apache.org/jira/browse/HDFS-1148
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode, performance
>            Reporter: Todd Lipcon
>            Assignee: Dave Thompson
>         Attachments: hdfs-1148-old.txt, hdfs-1148-trunk.txt, patch-HDFS-1148-rel0.20.2.txt
>
>
> In benchmarking HDFS-941 I noticed that for the random read workload, the FSDataset lock
is highly contended. After converting it to a ReentrantReadWriteLock, I saw a ~25% improvement
on both latency and ops/second.



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