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https://issues.apache.org/jira/browse/OAK-629?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jukka Zitting resolved OAK-629.
-------------------------------
Resolution: Fixed
Fix Version/s: 0.7
Assignee: Jukka Zitting
Done in revision 1448151.
> SegmentMK: Reverse writing of segments
> --------------------------------------
>
> Key: OAK-629
> URL: https://issues.apache.org/jira/browse/OAK-629
> Project: Jackrabbit Oak
> Issue Type: Sub-task
> Components: segmentmk
> Reporter: Jukka Zitting
> Assignee: Jukka Zitting
> Priority: Minor
> Fix For: 0.7
>
>
> By design changes to a content tree get written to a segment using a
> depth-first traversal. As a consequence the top-down access pattern used for
> reading content ends up parsing the content from the end to the beginning.
> This is somewhat troublesome as many memory and disk caches are optimized for
> the opposite direction of access.
> To better leverage cache prefetching features (like readahead in Linux), it
> would be useful to reverse the order in which segments get written. In other
> words, instead of filling the segment buffer from the beginning to the end as
> the depth-first traversal proceeds, we could fill the buffer from the end to
> the beginning and count segment offsets from the end of a segment instead of
> its beginning.
> While at it, it might also make sense to align record offsets at four or
> eight byte boundaries to further (micro-)optimize access. It might also be
> worth it to reduce the segment size limit to something like 512kB so we could
> squeeze record references down from four to three bytes.
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