From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755710Ab3JYDKY (ORCPT ); Thu, 24 Oct 2013 23:10:24 -0400 Received: from mail-vb0-f41.google.com ([209.85.212.41]:33632 "EHLO mail-vb0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754092Ab3JYDKX convert rfc822-to-8bit (ORCPT ); Thu, 24 Oct 2013 23:10:23 -0400 MIME-Version: 1.0 In-Reply-To: <20131023105931.GG1275@quack.suse.cz> References: <20131023105931.GG1275@quack.suse.cz> Date: Fri, 25 Oct 2013 11:10:22 +0800 Message-ID: Subject: Re: A thought about IO scheduler in linux kernel for SSD From: =?GB2312?B?uqvA2g==?= To: Jan Kara Cc: linux-kernel@vger.kernel.org Content-Type: text/plain; charset=GB2312 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2013/10/23 Jan Kara : > On Wed 23-10-13 08:47:44, º«ÀÚ wrote: >> Nowadays,the IO schedulers in linux kernel have four types: >> >> deadline,noop,Anticiptory and CFQ.CFQ is the default scheduler.But CFQ is >> not a good scheduler for SSD,dealine may be a good choice. > > That doesn't make much sense to me. If there are two bios in flight for > some sector, results are undefined. Thus we usually avoid such situation > (usually we want to have defined contents of the disk :). The exclusion is > usually achieved at higher level using page locking etc. So adding code > speeding up such requests doesn't seem worth it. > > Honza > -- > Jan Kara > SUSE Labs, CR Do you mean that the probability of two bios have the same start sector in request list at this level is very low??Discuss with you is a kind of enjoyment.