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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-8046) Allow better control of getContentSummary
Date Thu, 02 Apr 2015 17:15:53 GMT
Kihwal Lee created HDFS-8046:

             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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