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From Joey Echeverria <j...@cloudera.com>
Subject Re: performance: HLog flush to disk each thread, can we decrease IO calls?
Date Wed, 29 Jun 2011 13:08:06 GMT
Hey Mingjian,

This sounds like a good idea  Your patch didn't make it through. Would you mind either filing
a JIRA and uploading your patch there or at least posting it to something like pastebin so
we can take a look.

-Joey



On Jun 29, 2011, at 3:27, Mingjian Deng <koven2049@gmail.com> wrote:

> Hi:
>     We found that the hlog sync to disk each time. 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 40%.
> 
>     Just see the HLog.patch.
>     

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