From: Bart Van Assche <bvanassche@acm.org>
To: scameron@beardog.cce.hp.com
Cc: linux-scsi@vger.kernel.org, stephenmcameron@gmail.com, dab@hp.com
Subject: Re: SCSI mid layer and high IOPS capable devices
Date: Thu, 13 Dec 2012 12:40:27 +0100 [thread overview]
Message-ID: <50C9BEAB.6010702@acm.org> (raw)
In-Reply-To: <20121211224626.GB20898@beardog.cce.hp.com>
On 12/11/12 23:46, scameron@beardog.cce.hp.com wrote:
> I would be curious to see what kind of results you would get with scsi_debug
> with fake_rw=1. I am sort of suspecting that trying to put an "upper limit"
> on scsi LLD IOPS performance by seeing what scsi_debug will do with fake_rw=1
> is not really valid (or, maybe I'm doing it wrong) as I know of one case in
> which a real HW scsi driver beats scsi_debug fake_rw=1 at IOPS on the very
> same system, which seems like it shouldn't be possible. Kind of mysterious.
The test
# disable-frequency-scaling
# modprobe scsi_debug delay=0 fake_rw=1
# echo 2 > /sys/block/sdc/queue/rq_affinity
# echo noop > /sys/block/sdc/queue/scheduler
# echo 0 > /sys/block/sdc/queue/add_random
results in about 800K IOPS for random reads on the same setup (with a
request size of 4 KB; CPU: quad core i5-2400).
Repeating the same test with fake_rw=0 results in about 651K IOPS.
Bart.
next prev parent reply other threads:[~2012-12-13 11:40 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-11 0:00 SCSI mid layer and high IOPS capable devices scameron
2012-12-11 8:21 ` Bart Van Assche
2012-12-11 22:46 ` scameron
2012-12-13 11:40 ` Bart Van Assche [this message]
2012-12-13 18:03 ` scameron
2012-12-13 17:18 ` Bart Van Assche
2012-12-13 15:22 ` Bart Van Assche
2012-12-13 17:25 ` scameron
2012-12-13 16:47 ` Bart Van Assche
2012-12-13 16:49 ` Christoph Hellwig
2012-12-14 9:44 ` Bart Van Assche
2012-12-14 16:44 ` scameron
2012-12-14 16:15 ` Bart Van Assche
2012-12-14 19:55 ` scameron
2012-12-14 19:28 ` Bart Van Assche
2012-12-14 21:06 ` scameron
2012-12-15 9:40 ` Bart Van Assche
2012-12-19 14:23 ` Christoph Hellwig
2012-12-13 21:20 ` scameron
2012-12-14 0:22 ` Jack Wang
[not found] ` <CADzpL0TMT31yka98Zv0=53N4=pDZOc9+gacnvDWMbj+iZg4H5w@mail.gmail.com>
[not found] ` <006301cdd99c$35099b40$9f1cd1c0$@com>
[not found] ` <CADzpL0S5cfCRQftrxHij8KOjKj55psSJedmXLBQz1uQm_SC30A@mail.gmail.com>
2012-12-14 4:59 ` Jack Wang
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