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https://issues.apache.org/jira/browse/OAK-4015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15159040#comment-15159040
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Alex Parvulescu commented on OAK-4015:
--------------------------------------
one interesting thing: the {{monitor.tryEnter}} and {{monitor.tryEnterIf}} java
docs say "This method disregards the fairness setting of this monitor.", but
apparently {{commitSemaphore.tryAcquire}} also breaks fairness, so it's
probably a fair change :)
I'm having some issues grasping this bit {{monitor.getOccupiedDepth() == 1}},
there must be something that escapes me, would you mind sharing?
{code}
public void unlock() {
if (monitor.getOccupiedDepth() == 1) {
expedited.remove(currentThread());
}
monitor.leave();
}
{code}
> 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
>
> Attachments: OAK-4015-histo.png, OAK-4015-wait-time.png
>
>
> 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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