From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751184AbWDEJTu (ORCPT ); Wed, 5 Apr 2006 05:19:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751185AbWDEJTu (ORCPT ); Wed, 5 Apr 2006 05:19:50 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:47907 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S1751184AbWDEJTt (ORCPT ); Wed, 5 Apr 2006 05:19:49 -0400 Date: Wed, 5 Apr 2006 11:20:06 +0200 From: Jens Axboe To: Bill Davidsen Cc: Vishal Patil , Linux Kernel Mailing List Subject: Re: CSCAN I/O scheduler for 2.6.10 kernel Message-ID: <20060405092006.GA4117@suse.de> References: <4745278c0603301955w26fea42eid6bcab91c573eaa3@mail.gmail.com> <4745278c0603301958o4c2ed282x3513fdb459d8ec7c@mail.gmail.com> <4432D6D4.2020102@tmr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4432D6D4.2020102@tmr.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 04 2006, Bill Davidsen wrote: > Vishal Patil wrote: > >Maintain two queues which will be sorted in ascending order using Red > >Black Trees. When a disk request arrives and if the block number it > >refers to is greater than the block number of the current request > >being served add (merge) it to the first sorted queue or else add > >(merge) it to the second sorted queue. Keep on servicing the requests > >from the first request queue until it is empty after which switch over > >to the second queue and now reverse the roles of the two queues. > >Simple and Sweet. Many thanks for the awesome block I/O layer in the > >2.6 kernel. > > > Why both queues sorting in ascending order? I would think that one > should be in descending order, which would reduce the seek distance > between the last i/o on one queue and the first on the next. Then it wouldn't be CSCAN, now would it? :-) -- Jens Axboe