linux-kernel - Re: [RESEND] [PATCH] readahead:add blk_run_backing

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Date:	Mon, 29 Jun 2009 16:43:48 +0200
From:	Ronald Moesbergen <intercommit@...il.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Vladislav Bolkhovitin <vst@...b.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	"Alan.Brunelle@...com" <Alan.Brunelle@...com>,
	"hifumi.hisashi@....ntt.co.jp" <hifumi.hisashi@....ntt.co.jp>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"jens.axboe@...cle.com" <jens.axboe@...cle.com>,
	"randy.dunlap@...cle.com" <randy.dunlap@...cle.com>,
	Bart Van Assche <bart.vanassche@...il.com>
Subject: Re: [RESEND] [PATCH] readahead:add blk_run_backing_dev

2009/6/29 Wu Fengguang <fengguang.wu@...el.com>:
> On Mon, Jun 29, 2009 at 09:13:27PM +0800, Wu Fengguang wrote:
>> On Mon, Jun 29, 2009 at 09:04:57PM +0800, Vladislav Bolkhovitin wrote:
>> > Wu Fengguang, on 06/29/2009 04:54 PM wrote:
>> > >
>> > > Why not 2.6.30? :)
>> >
>> > We started with 2.6.29, so why not complete with it (to save additional
>> > Ronald's effort to move on 2.6.30)?
>>
>> OK, that's fair enough.
>
> btw, I backported the 2.6.31 context readahead patches to 2.6.29, just
> in case it will help the SCST performance.
>
> Ronald, if you run context readahead, please make sure that the server
> side readahead size is bigger than the client side readahead size.

I tried this patch on a vanilla kernel and no other patches applied,
but it does not seem to help. The iSCSI throughput does not go above
60MB/s. (1GB in 17 seconds). I have tried several readahead settings
from 128KB up to 4MB and kept the server readahead at twice the client
readahead, but it never comes above 60MB/s. This is using SCST on the
serverside and openiscsi on the client. I get much better throughput
(90 MB/s) when using the patches supplied with SCST, together with the
blk_run_backing_dev readahead patch.

Ronald.
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