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From "ryan rawson (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-3455) Heap fragmentation in region server
Date Wed, 26 Jan 2011 05:19:48 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12986853#action_12986853
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ryan rawson commented on HBASE-3455:
------------------------------------

for ICVs, we might be force flushing due to the maximum hlog fairly
'frequently' anyways.  if we spill to the next slab, will we let the
GC free up the previous slabs?  maybe once we fill up an allocation we
dereference the slab from the slab manager that way we can let GC do
the hard work for us?


> 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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