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From "Anastasia Braginsky (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-18056) Change CompactingMemStore in BASIC mode to merge multiple segments in pipeline
Date Wed, 17 May 2017 09:42:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18056?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16013797#comment-16013797
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Anastasia Braginsky commented on HBASE-18056:
---------------------------------------------

[~anoop.hbase], we have already done performance tests and we saw merge makes situation better.
What is the JIRA number where you explain the problems you see? Why do you think the merge
will make situation worse there? The merge is of CellArrayMaps only and is not related to
MSLAB at all.

bq. Reduction in GC when there are duplicated data right? PE kind of work load where each
of the data is diff key, how come this merge will reduce GC?

No, without duplicates. It reduces GC because the segments memory is garbage collected gradually
and not all together in time of flush. But the performance numbers speak by themselves.

> Change CompactingMemStore in BASIC mode to merge multiple segments in pipeline
> ------------------------------------------------------------------------------
>
>                 Key: HBASE-18056
>                 URL: https://issues.apache.org/jira/browse/HBASE-18056
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Anastasia Braginsky
>
> Under HBASE-16417 it was decided that CompactingMemStore in BASIC mode should merge multiple
ImmutableSegments in CompactionPipeline. Basic+Merge actually demonstrated reduction in GC,
alongside improvement in other metrics.
> However, the limit on the number of segments in pipeline is still set to 30. Under this
JIRA it should be changed to 1, as it was tested under HBASE-16417.



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