linux-kernel - Re: weird throughput on write to SATA disk

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Date:	Tue, 14 Oct 2008 21:10:49 +0200
From:	kenneth johansson <ken@...jo.org>
To:	Tejun Heo <tj@...nel.org>
Cc:	Grant Grundler <grundler@...gle.com>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: weird throughput on write to SATA disk

On Tue, 2008-10-14 at 18:17 +0900, Tejun Heo wrote:
> kenneth johansson wrote:
> > On Mon, 2008-10-13 at 18:33 -0700, Grant Grundler wrote:
> >> On Mon, Oct 13, 2008 at 3:19 PM, kenneth johansson <ken@...jo.org> wrote:
> >> ...
> >>>> Can you try "dd oflag=direct if=/dev/null of=/dev/sdb bs=64k"?
> >>> I changed to use O_DIRECT and it's much more consistent now. 69-75 with
> >>> 74 about 95% of the time.
> >> That's low but it could be worse. Many things can contribute to slow
> >> disks. 
> > Well my main problem was that it was fluctuating so much that can't be
> > right. 
> Can you try deadline scheduler?
> 

I did but it was so bad I restarted my computer and did it again. Same
result complete disaster. so fas O_DIRECT is the only one that is as it
should be.

Alan mentioned a patch by Arjan van de Ven anyone knows how to find that
one?



Download attachment "deadline2.png" of type "image/png" (5526 bytes)

Download attachment "direct.png" of type "image/png" (3778 bytes)