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https://issues.apache.org/jira/browse/OAK-4015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15148580#comment-15148580
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Michael Dürig commented on OAK-4015:
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Initial implementation of an expeditable lock:
https://github.com/mduerig/jackrabbit-oak/commit/8b9c9e598a60af14fe5fe791ff0dbe2fe646892c
In a quick test this brought the wait time of the compactor down to 7s from 22s
resulting in a total of 6 vs. 16 extra compaction cycles. (The test went
through 9 revision gc's in total).
While I still like to collect more evidence on the effect of this change, I'd
also be happy about a review mainly of {{ExpeditableLock}}.
> Expedite commits from the compactor
> -----------------------------------
>
> Key: OAK-4015
> URL: https://issues.apache.org/jira/browse/OAK-4015
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: segmentmk
> Reporter: Michael Dürig
> Labels: compaction, gc, perfomance
> Fix For: 1.6
>
>
> Concurrent commits during compaction cause those to be re-compacted.
> Currently it seems that the compaction thread can end up waiting for some
> time to acquire the commit lock [1], which in turn causes more commits to
> pile up to be re-compacted. I think this could be improved by tweaking the
> lock such that the compactor could jump ahead of the queue. I.e. use a lock
> which can be acquired in expedited mode.
> [1] SegmentNodeStore#commitSemaphore
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