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From Michael Dürig (JIRA) <j...@apache.org>
Subject [jira] [Commented] (OAK-4732) (Slightly) prioritise reads over writes
Date Thu, 01 Sep 2016 10:12:20 GMT

    [ https://issues.apache.org/jira/browse/OAK-4732?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15454986#comment-15454986
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Michael Dürig commented on OAK-4732:
------------------------------------

https://github.com/mduerig/jackrabbit-oak/commit/10245d091fc19092976e1f16eff9b088db182a99
is a POC showing where this could be going. A couple of experiments with {{SegmentCompactionIT}}
didn't show a significant impact of this. Needs more systematic evaluation. 

> (Slightly) prioritise reads over writes 
> ----------------------------------------
>
>                 Key: OAK-4732
>                 URL: https://issues.apache.org/jira/browse/OAK-4732
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: segment-tar
>            Reporter: Michael Dürig
>            Assignee: Michael Dürig
>              Labels: Performance
>             Fix For: Segment Tar 0.0.14
>
>
> When fetching the current root from the {{SegmentNodeStore}} an older revision will be
returned when a commit is being processed concurrently. I think it would make sense to wait
for a short time in this case increasing the chance of returning an up to date state. The
idea is that this would lower the rebasing work that need to be done later on should the returned
root be used for further modifications. 
> An interesting value for the wait time is to use  the median (or more general a percentile)
of the commit time of the last say 1000 commits. This would mean that (for the median) we
have a 50% chance of getting up to date date. For a 90% percentile we would have longer wait
times but then a 90% chance of getting up to date date. 



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