From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756481Ab2DJRov (ORCPT ); Tue, 10 Apr 2012 13:44:51 -0400 Received: from mail-wi0-f178.google.com ([209.85.212.178]:52589 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755503Ab2DJRou (ORCPT ); Tue, 10 Apr 2012 13:44:50 -0400 Message-ID: <4F84718C.4010706@gmail.com> Date: Tue, 10 Apr 2012 19:44:44 +0200 From: Xose Vazquez Perez MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] block: Change default IO scheduler to deadline except SATA Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vivek Goyal wrote: > I am wondering if CFQ as default scheduler is still the right choice. CFQ > generally works well on slow rotational media (SATA?). But often > underperforms on faster storage (storage arrays, PCIE SSDs, virtualized > disk in linux guests etc). People often put logic in user space to tune their > systems and change IO scheduler to deadline to get better performance on > faster storage. > > Though there is not one good answer for all kind of storage and for all > kind of workloads, I am wondering if we can provide a better default and > that is change default IO scheduler to "deadline" except SATA. > > One can argue that some SAS disks can be slow too and benefit from CFQ. Yes, > but default IO scheduler choice is not perfect anyway. It just tries to > cater to a wide variety of use cases out of the box. > > So I am throwing this patch out see if it flies. Personally, I think it > might turn out to be a more reasonable default. done time ago for dasd devices. chuchi:~/curre/linux-2.6 $ grep -ri deadline drivers/s390/block/* drivers/s390/block/dasd.c: rc = elevator_init(block->request_queue, "deadline"); drivers/s390/block/Kconfig: select IOSCHED_DEADLINE