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Date: Thu, 2 Apr 2015 17:15:53 +0000 (UTC)
From: "Kihwal Lee (JIRA)" <jira@apache.org>
To: hdfs-dev@hadoop.apache.org
Message-ID: <JIRA.12787738.1427994915000.108279.1427994953052@Atlassian.JIRA>
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Subject: [jira] [Created] (HDFS-8046) Allow better control of
 getContentSummary
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Kihwal Lee created HDFS-8046:
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             Summary: 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


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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