From: Jens Axboe <jens.axboe@oracle.com>
To: Richard Kennedy <richard@rsk.demon.co.uk>
Cc: fio <fio@vger.kernel.org>
Subject: Re: fio mmap writes much slower than default writes
Date: Sat, 18 Jul 2009 08:18:20 +0200 [thread overview]
Message-ID: <20090718061819.GF4148@kernel.dk> (raw)
In-Reply-To: <1247751607.2689.63.camel@localhost.localdomain>
On Thu, Jul 16 2009, Richard Kennedy wrote:
> Running tests of fio write with sizes that are less than the write cache
> size I'm seeing a big slow down when using mmap. I'm running the tests
> on linux 2.6.31-rc* x86_64.
>
> Typical results with default writes :-
>
> fio size=300m rw=write
> write: io=300MiB, bw=314MiB/s, iops=80,418, runt= 955msec
>
> with mmap :-
>
> fio size=300m rw=write ioengine=mmap
> write: io=300MiB, bw=55,732KiB/s, iops=13,933, runt= 5512msec
>
>
> Is this expected or is it indicative of a problem somewhere?
What does the full job file look like? Is the file cached, or are the
faults reading in data?
--
Jens Axboe
next prev parent reply other threads:[~2009-07-18 6:18 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-16 13:40 fio mmap writes much slower than default writes Richard Kennedy
2009-07-18 6:18 ` Jens Axboe [this message]
2009-07-18 13:58 ` Richard Kennedy
2009-07-18 14:20 ` Jens Axboe
2009-07-18 14:39 ` Jens Axboe
2009-07-18 14:50 ` Richard Kennedy
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