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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8046) Allow better control of getContentSummary
Date Thu, 09 Apr 2015 11:56:23 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8046?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14487252#comment-14487252
] 

Hudson commented on HDFS-8046:
------------------------------

SUCCESS: Integrated in Hadoop-Yarn-trunk #892 (See [https://builds.apache.org/job/Hadoop-Yarn-trunk/892/])
HDFS-8046. Allow better control of getContentSummary. Contributed by Kihwal Lee. (kihwal:
rev 285b31e75e51ec8e3a796c2cb0208739368ca9b8)
* hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ContentSummaryComputationContext.java
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirStatAndListingOp.java


> Allow better control of getContentSummary
> -----------------------------------------
>
>                 Key: HDFS-8046
>                 URL: https://issues.apache.org/jira/browse/HDFS-8046
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Kihwal Lee
>            Assignee: Kihwal Lee
>             Fix For: 2.8.0
>
>         Attachments: HDFS-8046.v1.patch
>
>
> On busy clusters, users performing quota checks against a big directory structure can
affect the namenode performance. It has become a lot better after HDFS-4995, but as clusters
get bigger and busier, it is apparent that we need finer grain control to avoid long read
lock causing throughput drop.
> Even with unfair namesystem lock setting, a long read lock (10s of milliseconds) can
starve many readers and especially writers. So the locking duration should be reduced, which
can be done by imposing a lower count-per-iteration limit in the existing implementation.
 But HDFS-4995 came with a fixed amount of sleep between locks. This needs to be made configurable,
so that {{getContentSummary()}} doesn't get exceedingly slow.



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