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From "Jay Booth (JIRA)" <j...@apache.org>
Subject [jira] Created: (HDFS-1323) Pool/share file channels for HDFS read
Date Fri, 30 Jul 2010 16:45:17 GMT
Pool/share file channels for HDFS read

                 Key: HDFS-1323
                 URL: https://issues.apache.org/jira/browse/HDFS-1323
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: data-node
            Reporter: Jay Booth
             Fix For: 0.20-append, 0.22.0

Currently, all reads in HDFS require opening and closing the underlying block/meta filechannels.
 We could pool these filechannels and save some system calls and other work.  Since HDFS read
requests can be satisfied by positioned reads and transferTos, we can even share these filechannels
between concurrently executing requests.

The attached patch was benchmarked as part of work on HDFS-918 and exhibited a 10% performance
increase for small random reads.

This does not affect client logic and involves minimal change to server logic.  Patch is based
on branch 20-append. 

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