linux-ext4 - Re: [PATCH] ext4: start seraching for the right extent from the goal group.

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Message-id: <20080502185319.GG2950@webber.adilger.int>
Date:	Fri, 02 May 2008 11:53:19 -0700
From:	Andreas Dilger <adilger@....com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	Eric Sandeen <sandeen@...hat.com>, linux-ext4@...r.kernel.org,
	cmm@...ibm.com, tytso@....edu
Subject: Re: [PATCH] ext4: start seraching for the right extent from the	goal
 group.

On May 01, 2008  21:07 +0530, Aneesh Kumar K.V wrote:
> On Wed, Apr 30, 2008 at 07:58:35AM -0500, Eric Sandeen wrote:
> > Aneesh Kumar K.V wrote:
> > > With mballoc we search for the best extent using different
> > > criteria. We should always use the goal group when we are
> > > starting with a new criteria.
> > 
> > Aneesh, is there any testcase etc that will demonstrate the resulting
> > difference in layout?
> > 
> > It's not clear to me from this changelog (without looking at a lot more
> > context) exactly what you're changing and why...
> 
> I don't have any specific test case.  With mballoc depending on the
> request size we follow different criteria to allocate blocks. For
> example if the size is stripe size multiple we use criteria 1 and start
> searching for the right blocks from block group starting with goal
> group. If we don't find right count of blocks, we use criteria 2 and start
> searching from the group block 0. I guess with criteria 2 also, we should start
> searching from the goal group so that when we find the right count of
> blocks we find them close to the goal group.

This makes sense to me.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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