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From "chunhui shen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6466) Enable multi-thread for memstore flush
Date Tue, 21 Aug 2012 05:35:38 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6466?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13438468#comment-13438468
] 

chunhui shen commented on HBASE-6466:
-------------------------------------

@Jimmy
Flushing multiple regions each time could only help a little, about increase 5% flush ability
because we select a region to flush is very fast.

I agree with one flush thread is enough in most case, however we have encountered the case
that memstore always at the global limit in the online application, the small affect is writing
will be blocked sometimes and the serious affect is jvm would always do CMS if your configuration
is not very appropriate
                
> Enable multi-thread for memstore flush
> --------------------------------------
>
>                 Key: HBASE-6466
>                 URL: https://issues.apache.org/jira/browse/HBASE-6466
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: chunhui shen
>            Assignee: chunhui shen
>         Attachments: HBASE-6466.patch, HBASE-6466v2.patch, HBASE-6466v3.patch
>
>
> If the KV is large or Hlog is closed with high-pressure putting, we found memstore is
often above the high water mark and block the putting.
> So should we enable multi-thread for Memstore Flush?
> Some performance test data for reference,
> 1.test environment : 
> random writting;upper memstore limit 5.6GB;lower memstore limit 4.8GB;400 regions per
regionserver;row len=50 bytes, value len=1024 bytes;5 regionserver, 300 ipc handler per
regionserver;5 client, 50 thread handler per client for writing
> 2.test results:
> one cacheFlush handler, tps: 7.8k/s per regionserver, Flush:10.1MB/s per regionserver,
appears many aboveGlobalMemstoreLimit blocking
> two cacheFlush handlers, tps: 10.7k/s per regionserver, Flush:12.46MB/s per regionserver,
> 200 thread handler per client & two cacheFlush handlers, tps:16.1k/s per regionserver,
Flush:18.6MB/s per regionserver

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