From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 23 Mar 2003 07:07:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 23 Mar 2003 07:07:53 -0500 Received: from 205-158-62-158.outblaze.com ([205.158.62.158]:18658 "HELO spf1.us.outblaze.com") by vger.kernel.org with SMTP id ; Sun, 23 Mar 2003 07:07:50 -0500 Message-ID: <20030323121850.48607.qmail@mail.com> Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-Mailer: MIME-tools 5.41 (Entity 5.404) From: "Subodh S" To: linux-kernel@vger.kernel.org Cc: linux-scsi@vger.kernel.org Date: Sun, 23 Mar 2003 07:18:50 -0500 Subject: Servicing of requests X-Originating-Ip: 203.124.128.117 X-Originating-Server: ws1-1.us4.outblaze.com Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, Whenever I read data of 'x'k size using one read() system call, I find batches of some 'y' no. of make_requests calls followed by the same no. of end_io's. Something like : make_req make_req make_req end_io end_io end_io make_req make_req make_req end_io end_io end_io The output above gives me an idea that 3(hypothetical no.) buffer_heads above form a request. (since 1 make_request corresponds to 1 buffer_head) and maybe since 1 request is serviced at a time I can see 3 make_req's together. Is my understanding right ?? But, I have read that sd uses some optimization algorithm to club requests so that the disk seek time is reduced. In which case since all requests are to adjecents sectors it should create a single request of all 'x'k assuming 1 buffer_head is of size 1k. Does this make sense ?? -subodh -- __________________________________________________________ Sign-up for your own FREE Personalized E-mail at Mail.com http://www.mail.com/?sr=signup