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From Michael Dürig (JIRA) <j...@apache.org>
Subject [jira] [Created] (OAK-3330) FileStore lock contention with concurrent writers
Date Wed, 02 Sep 2015 07:26:45 GMT
Michael Dürig created OAK-3330:

             Summary: FileStore lock contention with concurrent writers
                 Key: OAK-3330
                 URL: https://issues.apache.org/jira/browse/OAK-3330
             Project: Jackrabbit Oak
          Issue Type: Improvement
          Components: segmentmk
            Reporter: Michael Dürig
            Assignee: Michael Dürig

Concurrently writing to the file store can lead to a sever lock contention in {{FileStore#readSegment}}.
That method searches the current {{TarWriter}} instance for the segment once it could not
be found in any of the {{TarReader}} instances. This is the point where synchronizes on the
{{FileStore}} instance, which leads to  the contention. 
The effect is only observable once the segment cache becomes full and reads actually need
to go to the file store. Thus a possible improvement could be to pin segments from the current
tar writer to the cache. Alternatively we could try to ease locking by employing read/write
locks where possible. 

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