From: Jens Axboe <jens.axboe@oracle.com>
To: Paolo Valente <paolo.valente@unimore.it>
Cc: Pavel Machek <pavel@ucw.cz>, linux-kernel@vger.kernel.org
Subject: Re: [RESEND][RFC] BFQ I/O Scheduler
Date: Thu, 17 Apr 2008 09:10:12 +0200 [thread overview]
Message-ID: <20080417071012.GP12774@kernel.dk> (raw)
In-Reply-To: <4806EACB.7040408@unimore.it>
On Thu, Apr 17 2008, Paolo Valente wrote:
> Pavel Machek ha scritto:
> >
> >>In the first type of tests, to achieve a higher throughput than CFQ
> >>(with the default 100 ms time slice), the maximum budget for BFQ
> >>had to be set to at least 4k sectors. Using the same value for the
> >>
> >
> >Hmm, 4k sectors is ~40 seconds worst case, no? That's quite long...
> >
> Actually, in the worst case among our tests, the aggregate throughput
> with 4k sectors was ~ 20 MB/s, hence the time for 4k sectors ~ 4k * 512
> / 20M = 100 ms.
That's not worse case, it is pretty close to BEST case. Worst case is 4k
of sectors, with each being a 512b IO and causing a full stroke seek.
For that type of workload, even a modern sata hard drive will be doing
500kb/sec or less. That's rougly a thousand sectors per seconds, so ~4
seconds worst case for 4k sectors.
--
Jens Axboe
next prev parent reply other threads:[~2008-04-17 7:10 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-01 15:29 [RESEND][RFC] BFQ I/O Scheduler Fabio Checconi
2008-04-15 8:22 ` Jens Axboe
2008-04-15 9:11 ` Fabio Checconi
2008-04-15 12:42 ` Jens Axboe
2008-04-15 18:08 ` Fabio Checconi
2008-04-16 6:48 ` Paolo Valente
2008-04-18 1:26 ` Aaron Carroll
2008-04-16 18:44 ` Pavel Machek
2008-04-17 6:14 ` Paolo Valente
2008-04-17 7:10 ` Jens Axboe [this message]
2008-04-17 8:26 ` Paolo Valente
2008-04-17 8:30 ` Jens Axboe
2008-04-17 9:24 ` Paolo Valente
2008-04-17 9:27 ` Jens Axboe
2008-04-17 10:19 ` Aaron Carroll
2008-04-17 10:21 ` Jens Axboe
2008-04-17 11:30 ` Fabio Checconi
2008-04-17 15:19 ` Avi Kivity
2008-04-17 15:47 ` Paolo Valente
2008-04-17 15:51 ` Avi Kivity
2008-04-17 18:12 ` Paolo Valente
2008-04-17 23:44 ` Aaron Carroll
2008-04-17 10:24 ` Aaron Carroll
2008-04-17 11:14 ` Fabio Checconi
2008-04-17 12:14 ` Aaron Carroll
2008-04-17 13:54 ` Jens Axboe
2008-04-17 15:18 ` Paolo Valente
2008-04-17 8:48 ` Pavel Machek
2008-04-17 8:57 ` Jens Axboe
2008-04-17 9:14 ` Fabio Checconi
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