linux-kernel - Re: General question (scheduler) with SSDs?

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Date:	Fri, 20 Feb 2009 12:16:42 +0100
From:	Kay Sievers <kay.sievers@...y.org>
To:	Sitsofe Wheeler <sitsofe@...oo.com>
Cc:	Justin Piszcz <jpiszcz@...idpixels.com>,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	linux-raid@...r.kernel.org
Subject: Re: General question (scheduler) with SSDs?

On Fri, Feb 20, 2009 at 10:43, Sitsofe Wheeler <sitsofe@...oo.com> wrote:
> Whoops, I didn't mean to send that previous half formed mail :) Sorry.
>
> On Thu, Feb 19, 2009 at 08:38:38AM -0500, Justin Piszcz wrote:
>>
>> I was curious if anyone had done any benchmarks and/or has conclusive
>> information, what is the best Linux scheduler to use with SSDs?
>>
>> Noop?
>> CFQ?
>> AS?
>> Deadline?
>
> As mentioned in another mail there was a discussion on
> http://lkml.org/lkml/2009/1/31/28 and long thread talking about the
> introduction of the rotational flag here
> http://lkml.org/lkml/2009/1/5/340 . Cheapo SSDs or even USB keys are not
> auto detected as non-rotational devices by the kernel and after a bit of
> poking about I've come up with the following udev rules for my
> particular cases:
>
> SUBSYSTEM=="block", TEST=="/sys$devpath/queue/rotational", ATTRS{model}=="ASUS-PHISON *", RUN+="/bin/sh -c 'echo 0 > /sys$devpath/queue/rotational'"

Udev can write to the attribute itself. This should be all you need:
  SUSBSYTEM=="block", ATTRS{model}=="ASUS-PHISON *", ATTR{queue/rotational}="1"

Kay
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