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From "Liang Xie (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-6109) let sync_file_range() system call run in backgroud
Date Mon, 17 Mar 2014 09:44:42 GMT
Liang Xie created HDFS-6109:

             Summary: let sync_file_range() system call run in backgroud
                 Key: HDFS-6109
                 URL: https://issues.apache.org/jira/browse/HDFS-6109
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: datanode
    Affects Versions: 2.3.0, 3.0.0
            Reporter: Liang Xie
            Assignee: Liang Xie

Through we passed SYNC_FILE_RANGE_WRITE to sync_file_range, to make it as asynchronous as
possible, it still could be blocked, e.g. the os io request queue is full.
Since we use sync_file_range just as a page cache advisor role:) it doesn't decide or guarantee
the real durability, it would be nice if we could run it in  backgroud. At least my test log
showed, a few sync_file_range calls still cost tens of ms or more, due to the happened location
is in the critical write path(BlockReceiver class), from a upper view, like HBase application,
will "hung" tens of ms as well during Hlog syncing.
Generally speaking, the patch could not improve too much, but, better than before, right ?

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