From: Vladislav Bolkhovitin <vst@vlnb.net>
To: Wu Fengguang <wfg@linux.intel.com>
Cc: Jens Axboe <jens.axboe@oracle.com>,
Jeff Moyer <jmoyer@redhat.com>,
"Vitaly V. Bursov" <vitalyb@telenet.dn.ua>,
linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org,
lukasz.jurewicz@gmail.com
Subject: Re: Slow file transfer speeds with CFQ IO scheduler in some cases
Date: Fri, 20 Mar 2009 11:53:34 +0300 [thread overview]
Message-ID: <49C3598E.4010704@vlnb.net> (raw)
In-Reply-To: <49C2846D.5030500@vlnb.net>
Vladislav Bolkhovitin, on 03/19/2009 08:44 PM wrote:
> 6. Unexpected result. In case, when all IO threads work in the same IO
> context with CFQ increasing RA size *decreases* throughput. I think this
> is, because RA requests performed as single big READ requests, while
> requests coming from remote clients are much smaller in size (up to
> 256K), so, when the read by RA data transferred to the remote client on
> 100MB/s speed, the backstorage media gets rotated a bit, so the next
> read request must wait the rotation latency (~0.1ms on 7200RPM).
^^^^^^^^^^^^^^^^^
Oops, it's RP*M*, hence the full rotation latency is in 60 times more,
i.e. 8.3 ms.
Sorry,
Vlad
next prev parent reply other threads:[~2009-03-20 8:52 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20081112190227.GS26778@kernel.dk>
[not found] ` <1226566313.199910.29888@de>
[not found] ` <492BDAA9.4090405@vlnb.net>
[not found] ` <20081125113048.GB16422@localhost>
[not found] ` <492BE47B.3010802@vlnb.net>
[not found] ` <20081125114908.GA16545@localhost>
[not found] ` <492BE97A.3050606@vlnb.net>
[not found] ` <492BEAE8.9050809@vlnb.net>
[not found] ` <20081125121534.GA16778@localhost>
[not found] ` <492EDCFB.7080302@vlnb.net>
[not found] ` <492EDCFB.7080302-d+Crzxg7Rs0@public.gmane.org>
2008-11-28 0:48 ` Slow file transfer speeds with CFQ IO scheduler in some cases Wu Fengguang
2009-02-12 18:35 ` Vladislav Bolkhovitin
2009-02-13 1:57 ` Wu Fengguang
2009-02-13 20:08 ` Vladislav Bolkhovitin
[not found] ` <4995D339.5050502-d+Crzxg7Rs0@public.gmane.org>
2009-02-16 2:34 ` Wu Fengguang
2009-02-17 19:03 ` Vladislav Bolkhovitin
2009-02-18 18:14 ` Vladislav Bolkhovitin
2009-02-19 1:35 ` Wu Fengguang
2009-02-17 19:01 ` Vladislav Bolkhovitin
2009-02-19 2:05 ` Wu Fengguang
2009-03-19 17:44 ` Vladislav Bolkhovitin
2009-03-20 8:53 ` Vladislav Bolkhovitin [this message]
2009-03-23 1:42 ` Wu Fengguang
2009-04-21 18:18 ` Vladislav Bolkhovitin
2009-04-24 8:43 ` Wu Fengguang
2009-05-12 18:13 ` Vladislav Bolkhovitin
[not found] ` <49946BE6.1040005-d+Crzxg7Rs0@public.gmane.org>
2009-02-17 19:01 ` Vladislav Bolkhovitin
[not found] ` <499B0979.8050006-d+Crzxg7Rs0@public.gmane.org>
2009-02-19 1:38 ` Wu Fengguang
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