linux-kernel - Re: 2.6.20-rc2+: CFQ halving disk throughput.

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Date:	Tue, 2 Jan 2007 18:09:17 +0100 (MET)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Mark Lord <lkml@....ca>
cc:	Jens Axboe <jens.axboe@...cle.com>,
	Rene Herman <rene.herman@...il.com>,
	Tejun Heo <htejun@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...l.org>
Subject: Re: 2.6.20-rc2+: CFQ halving disk throughput.


On Jan 2 2007 10:01, Mark Lord wrote:
> Jens Axboe wrote:
>> 
>> > But surely one of (not sure which) sync+async or async+sync may also
>> > be okay?
>> > Or would it?
>> 
>> Async merge to sync request should be ok. But I wonder what happens with
>> hdparm, since it seems to trigger one of these tests. Very puzzling.
>> I'll dive in and take a look.
>
> The code (written 10 years ago) isn't the best in the world,
> and will be redone entirely for hdparm-7.0 this year.
>
> But right now, it essentially does this:
>
> loop:
> seek( to sector zero );
> read( 2MBytes );
> repeat loop for 3 seconds

Well for pure reading speed, I already use  dd_rescue -d /dev/hda /dev/null
Gives the same as hdparm -t when acting on uncached data.


	-`J'
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