From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754103AbZBCXqF (ORCPT ); Tue, 3 Feb 2009 18:46:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751771AbZBCXpy (ORCPT ); Tue, 3 Feb 2009 18:45:54 -0500 Received: from smtp4.ono.com ([62.42.230.177]:11053 "EHLO resmaa15.ono.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751046AbZBCXpy (ORCPT ); Tue, 3 Feb 2009 18:45:54 -0500 X-Greylist: delayed 347 seconds by postgrey-1.27 at vger.kernel.org; Tue, 03 Feb 2009 18:45:53 EST Date: Wed, 4 Feb 2009 00:40:03 +0100 From: "J.A. =?UTF-8?B?TWFnYWxsw7Nu?=" To: Linux-Kernel Subject: Re: SSD and IO schedulers Message-ID: <20090204004003.26068f72@werewolf.home> In-Reply-To: <4dcf7d360901301355l7ed26a5aob7ef6d79d9607b6b@mail.gmail.com> References: <4dcf7d360901301355l7ed26a5aob7ef6d79d9607b6b@mail.gmail.com> X-Mailer: Claws Mail 3.7.0cvs53 (GTK+ 2.15.3; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 30 Jan 2009 22:55:47 +0100, Lorenzo Allegrucci wrote: > Hi, I was wondering how IO schedulers such as as-iosched, deadline and > cfq behave on SSD > (that have virtually no seek time), from a theoretical point of view. > How do they affect > performance on these devices? > I heard that the noop scheduler is often chosen by owners of EeePcs > (with a SSD unit). I'm beginning to think this is a _very_ bad idea. I have an AspireOne A110 (512MB, 8GB SSD). This is 'not the best SSD in the world', to say something. I had been booting with elevator=noop, because of all those advices found along many blogs. The fact is that the system behaved well, except when I was doing an 'urpmi --auto-update' (I use Mandriva). The bulk of rpm work rendered the box unusable. 5-10 seconds stalls and so on. After reading this, I killed the elevator option from grub, the system uses the default cfq scheduler, and things are much smoother and the laptop is perfectly usable while doing an update. I think even rpm itself works faster. Perhaps the reason is that, as the SSD is not so good, it behaves more like a rotational drive ;). > They report superior performance by using this (quite simple) scheduler. > Are there any scientific benchmarks around? > A couple questions: - Apart from noop, which scheduler do you think is the best for SSDs ? - I'm running 2.6.28.2. Does it have the 'SSD detector' in libata ? How can I verify it ? TIA -- J.A. Magallon \ Software is like sex: \ It's better when it's free Mandriva Linux release 2009.1 (Cooker) for x86_64 Linux 2.6.28.2-desktop-1mnb (gcc 4.3.2 (GCC) #1 Wed Jan