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From "mingjian (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4044) [performance]decrease IO calls when flush hlog
Date Thu, 30 Jun 2011 03:25:28 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13057598#comment-13057598
] 

mingjian commented on HBASE-4044:
---------------------------------

Oh...It's not really decrease IO calls.

> [performance]decrease IO calls when flush hlog
> ----------------------------------------------
>
>                 Key: HBASE-4044
>                 URL: https://issues.apache.org/jira/browse/HBASE-4044
>             Project: HBase
>          Issue Type: Improvement
>          Components: performance, regionserver
>            Reporter: mingjian
>            Assignee: mingjian
>             Fix For: 0.90.4
>
>         Attachments: HLog-trunk-v1.patch
>
>
>     We found that the hlog flush to disk would block other write threads. When one thread
exec "doWrite(info, logKey, edit);", the others wait for "updateLock" in HLog.java.
>     Why not the others add their edits into a list and wait. When sync's time, the whole
list sync to disk once. I think it will decrease the IO calls. 
>     So Maybe we will make two lists for edits. Each thread write to the "waledits" and
wait for "updateLock". Each thread can copy the "waledits" to "flushedits" and flush the "flushedits"
to disk once it gets "updateLock".
>     In my test, it can increase the write speed of 100% when I set "hbase.regionserver.handler.count"=100.

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