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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-3455) Heap fragmentation in region server
Date Wed, 26 Jan 2011 06:04:45 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12986858#action_12986858
] 

stack commented on HBASE-3455:
------------------------------

@Ryan Your idea will only work if the slab is full of ICVs all with same coordinates, is that
right?  Or you thinking something different?  What if we did give each ICV a 2MB slab (or
less) and then when it overflowed, we'd let go of the old slab as you suggest?

@Todd I don't think the rewrite of a slab would be that bad perf-wise

@Tatsuya IIRC, we used to do iCVs this way but we'd end up flushing way too much; thats when
the replacing old values was putting into effect.

> Heap fragmentation in region server
> -----------------------------------
>
>                 Key: HBASE-3455
>                 URL: https://issues.apache.org/jira/browse/HBASE-3455
>             Project: HBase
>          Issue Type: Brainstorming
>          Components: performance, regionserver
>            Reporter: Todd Lipcon
>            Priority: Critical
>         Attachments: collapse-arrays.patch, HBasefragmentation.pdf, icv-frag.png, mslab-1.txt,
parse-fls-statistics.py, with-kvallocs.png
>
>
> Stop-the-world GC pauses have long been a problem in HBase. "Concurrent mode failures"
can usually be tuned around by setting the initiating occupancy fraction low, but eventually
the heap becomes fragmented and a promotion failure occurs.
> This JIRA is to do research/experiments about the heap fragmentation issue and possible
solutions.

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