From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261815AbULaDdS (ORCPT ); Thu, 30 Dec 2004 22:33:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261812AbULaDdS (ORCPT ); Thu, 30 Dec 2004 22:33:18 -0500 Received: from wproxy.gmail.com ([64.233.184.200]:51346 "EHLO wproxy.gmail.com") by vger.kernel.org with ESMTP id S261815AbULaDdA (ORCPT ); Thu, 30 Dec 2004 22:33:00 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:mime-version:content-type:content-transfer-encoding; b=hNH4QW9DpRgi3CG9cqcAlNkJkGhMsiH5mscFSZGP9t21rh1gMLLQkG4ExiD33AZjkeaEoXLWwg/c/kgzfu+VEcITPkLeAxOtye4VNQWpdWxiz3TNPfIhRgaWQACJqkz3DQzYWCnCFPvmgxZQ48NoUzyV/LJEj+s5WSKxp7SxzCY= Message-ID: <169c13c404123019322a766f64@mail.gmail.com> Date: Fri, 31 Dec 2004 04:32:59 +0100 From: Felipe Erias Reply-To: Felipe Erias To: linux-kernel@vger.kernel.org Subject: Queues when accessing disks Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, I'm trying to apply queuing theory to the study of the GNU/Linux kernel. Right now, I'm focusing in the queue of processes that appears when they try to access an I/O device (specifically, an IDE HD). When they want to read data, it behaves as a usual queue: several clients (processes) that require attention from a server (disk / driver / ...). The case when they want to write data is a bit more tricky, because of the cache buffers used by the OS, and maybe could be modelized by a network of queues. Both cases are interesting for my work, but I'll take the reading one first, just because it seems a bit more simple 'a priori'. To modelize the queue, I need to get some information: - what processes claim attention from the disk - when they do it - when they begin to be served - when they finish being served To get all this information, maybe I could hack my kernel a bit to write a line to a log on every access to the HD, or account the IRQs from the IDE channels... I also have the feeling that this queuing problem could dissappear o became more hidden if DMA were enabled. To be true, I'm a bit lost and that's why I ask for your help. Yours sincerely, Felipe Erias