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Date: Thu, 22 Jan 2009 23:03:20 -0500
From: Mathieu Desnoyers <compudj@...stal.dyndns.org>
To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: linux-kernel@...r.kernel.org, ltt-dev@...ts.casi.polymtl.ca,
Jens Axboe <jens.axboe@...cle.com>, akpm@...ux-foundation.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Ingo Molnar <mingo@...e.hu>
Subject: Re: [ltt-dev] [RFC PATCH] block: Fix bio merge induced high I/O
latency
* KOSAKI Motohiro (kosaki.motohiro@...fujitsu.com) wrote:
> > So, I ran the tests with my corrected patch, and the results are very
> > good !
> >
> > "incoming ssh connexion" test
> >
> > "config 2.6.28 cfq"
> > Linux 2.6.28
> > /sys/block/sd{a,b}/device/queue_depth = 31 (default)
> > /sys/block/sd{a,b}/queue/iosched/slice_async_rq = 2 (default)
> > /sys/block/sd{a,b}/queue/iosched/quantum = 4 (default)
> >
> > "config 2.6.28.1-patch1"
> > Linux 2.6.28.1
> > Corrected cfq patch applied
> > echo 1 > /sys/block/sd{a,b}/device/queue_depth
> > echo 1 > /sys/block/sd{a,b}/queue/iosched/slice_async_rq
> > echo 1 > /sys/block/sd{a,b}/queue/iosched/quantum
> >
> > On /dev/sda :
> >
> > I/O scheduler runt-min (msec) runt-max (msec)
> > cfq (2.6.28 cfq) 523 6637
> > cfq (2.6.28.1-patch1) 579 2082
> >
> > On raid1 :
> >
> > I/O scheduler runt-min (msec) runt-max (msec)
> > cfq (2.6.28 cfq) 523 28216
> > cfq (2.6.28.1-patch1) 517 3086
>
> Congraturation.
> In university machine room (at least, the university in japan),
> parallel ssh workload freqently happend.
>
> I like this patch :)
>
Please see my today's posts with numbers taken after my Seagate firmware
upgrade. The runt-max case is pretty hard to trigger "for sure" and I
had to do a few runs to trigger the problem. The latest tests are
better. E.g. the 3086msec is actually just because the problem has not
been hit.
But the
echo 1 > /sys/block/sd{a,b}/device/queue_depth
echo 1 > /sys/block/sd{a,b}/queue/iosched/slice_async_rq
echo 1 > /sys/block/sd{a,b}/queue/iosched/quantum
Are definitely helping a lot, as my last numbers also show. The patch,
OTOH, degraded performances rather than making them better.
Mathieu
>
>
> >
> > It looks like we are getting somewhere :) Are there any specific
> > queue_depth, slice_async_rq, quantum variations you would like to be
> > tested ?
> >
> > For reference, I attach my ssh-like job file (again) to this mail.
> >
> > Mathieu
> >
> >
> > [job1]
> > rw=write
> > size=10240m
> > direct=0
> > blocksize=1024k
> >
> > [global]
> > rw=randread
> > size=2048k
> > filesize=30m
> > direct=0
> > bsrange=4k-44k
> >
> > [file1]
> > startdelay=0
> >
> > [file2]
> > startdelay=4
> >
> > [file3]
> > startdelay=8
> >
> > [file4]
> > startdelay=12
> >
> > [file5]
> > startdelay=16
> >
> > [file6]
> > startdelay=20
> >
> > [file7]
> > startdelay=24
> >
> > [file8]
> > startdelay=28
> >
> > [file9]
> > startdelay=32
> >
> > [file10]
> > startdelay=36
> >
> > [file11]
> > startdelay=40
> >
> > [file12]
> > startdelay=44
> >
> > [file13]
> > startdelay=48
> >
> > [file14]
> > startdelay=52
> >
> > [file15]
> > startdelay=56
> >
> > [file16]
> > startdelay=60
> >
> > [file17]
> > startdelay=64
> >
> > [file18]
> > startdelay=68
> >
> > [file19]
> > startdelay=72
> >
> > [file20]
> > startdelay=76
> >
> > [file21]
> > startdelay=80
> >
> > [file22]
> > startdelay=84
> >
> > [file23]
> > startdelay=88
> >
> > [file24]
> > startdelay=92
> >
> > [file25]
> > startdelay=96
> >
> > [file26]
> > startdelay=100
> >
> > [file27]
> > startdelay=104
> >
> > [file28]
> > startdelay=108
> >
> > [file29]
> > startdelay=112
> >
> > [file30]
> > startdelay=116
> >
> > [file31]
> > startdelay=120
> >
> > [file32]
> > startdelay=124
> >
> > [file33]
> > startdelay=128
> >
> > [file34]
> > startdelay=132
> >
> > [file35]
> > startdelay=134
> >
> > [file36]
> > startdelay=138
> >
> > [file37]
> > startdelay=142
> >
> > [file38]
> > startdelay=146
> >
> > [file39]
> > startdelay=150
> >
> > [file40]
> > startdelay=200
> >
> > [file41]
> > startdelay=260
> >
> > --
> > Mathieu Desnoyers
> > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
> >
> > _______________________________________________
> > ltt-dev mailing list
> > ltt-dev@...ts.casi.polymtl.ca
> > http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
>
>
>
>
> _______________________________________________
> ltt-dev mailing list
> ltt-dev@...ts.casi.polymtl.ca
> http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
>
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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