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Posted to oak-issues@jackrabbit.apache.org by "Michael Dürig (JIRA)" <ji...@apache.org> on 2016/11/01 09:36:00 UTC

[jira] [Created] (OAK-5042) Improve caching of segments

Michael Dürig created OAK-5042:
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             Summary: Improve caching of segments
                 Key: OAK-5042
                 URL: https://issues.apache.org/jira/browse/OAK-5042
             Project: Jackrabbit Oak
          Issue Type: Improvement
          Components: segment-tar
            Reporter: Michael Dürig
            Assignee: Michael Dürig
             Fix For: 1.5.13


Various aspects of how Segment Tar caches segments could possibly improved. The current cache is a result of replacing the former ad-hoc cache with a proper one in OAK-3055. While the former was prone to contention under concurrent load the current cache is too oblivious about reads: read accesses are always served through {{SegmentId.segment}} and never actually hit the cache. This results in frequently accessed segments not to be seen as such by the cache and potentially being prematurely evicted. 

Possibly approaches to address this problem include: 
* Reinstantiating the cache we had pre OAK-3055 but making in fully concurrent. 
* Convey the information about read accesses to the current cache. 
* In either of the above cases avoid bulk segments from being placed into the cache. 



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