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https://issues.apache.org/jira/browse/HBASE-4044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13057230#comment-13057230
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Ted Yu commented on HBASE-4044:
-------------------------------
Great findings mingjian.
Do we need the check here ?
{code}
+ private void changeToFlush(){
+ if(flushEdits.isEmpty() == false)
+ flushEdits.clear();
{code}
We can call ArrayList.addAll() later in the routine.
I prefer clearing flushEdits after its contents are flushed for better GC. This
is my personal opinion.
> [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
> Fix For: 0.90.4
>
> Attachments: HLog.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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