linux-ext4 - Re: ext4

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Message-ID: <20120627193034.GA3198@thunk.org>
Date:	Wed, 27 Jun 2012 15:30:34 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	Ric Wheeler <ricwheeler@...il.com>, Fredrick <fjohnber@...o.com>,
	Ric Wheeler <rwheeler@...hat.com>, linux-ext4@...r.kernel.org,
	Andreas Dilger <adilger@...ger.ca>, wenqing.lz@...bao.com
Subject: Re: ext4_fallocate

On Tue, Jun 26, 2012 at 04:44:08PM -0400, Eric Sandeen wrote:
> > 
> > I tried running this fio recipe on v3.3, which I think does a decent job of
> > emulating the situation (fallocate 1G, do random 1M writes into it, with
> > fsyncs after each):
> > 
> > [test]
> > filename=testfile
> > rw=randwrite
> > size=1g
> > filesize=1g
> > bs=1024k
> > ioengine=sync
> > fallocate=1
> > fsync=1

A better workload would be to use a blocksize of 4k.  By using a
blocksize of 1024k, it's not surprising that the metadata overhead is
in the noise.

Try something like this; this will cause the extent tree overhead to
be roughly equal to the data block I/O.

[global]
rw=randwrite
size=128m
filesize=1g
bs=4k
ioengine=sync
fallocate=1
fsync=1

[thread1]
filename=testfile

					- Ted
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