linux-ext4 - Re: ext3 sequential read performance (~20%) degrade

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Message-Id: <1158336104.31501.2.camel@dyn9047017100.beaverton.ibm.com>
Date:	Fri, 15 Sep 2006 09:01:44 -0700
From:	Badari Pulavarty <pbadari@...ibm.com>
To:	suparna@...ibm.com
Cc:	Andrew Morton <akpm@...l.org>, sct@...hat.com,
	ext4 <linux-ext4@...r.kernel.org>
Subject: Re: ext3 sequential read performance (~20%) degrade

On Fri, 2006-09-15 at 11:20 +0530, Suparna Bhattacharya wrote:
> On Thu, Sep 14, 2006 at 05:03:08PM -0700, Andrew Morton wrote:
> > On Thu, 14 Sep 2006 16:36:12 -0700
> > Badari Pulavarty <pbadari@...ibm.com> wrote:
> > 
> > > Hi Andrew,
> > > 
> > > I have been working on tracking down ~20% performance degrade for
> > > sequential read performance for ext3. 
> > 
> > oop.  I'd kinda prefer that we discover things like this before the patch
> > gets into mainline.
> > 
> > > Finally narrowed it down to get_blocks() support. If I force
> > > ext3_get_blocks_handle() to always return 1 block - I get better
> > > IO rate. I did all the usual stuff, tracked down requests, traced
> > > blocksizes, looked at readahead code, looked at mpage_readpages()
> > > etc.. I still can't figure out how to explain the degrade..
> > > 
> > > Any suggestions on how to track it down.
> > 
> > Learn to driver Jens's blktrace stuff, find out why the IO scheduling went
> > bad.
> > 
> > Number one suspicion: the buffer_boundary() stuff isn't working.
> 
> I think you are right about that  - perhaps something along
> the lines of the following patch (untested) would help ?

Yep. It works :)

Thanks,
Badari



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