Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932506AbWEBIT7 (ORCPT ); Tue, 2 May 2006 04:19:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932505AbWEBIT7 (ORCPT ); Tue, 2 May 2006 04:19:59 -0400 Received: from smtp.ustc.edu.cn ([202.38.64.16]:28347 "HELO ustc.edu.cn") by vger.kernel.org with SMTP id S932506AbWEBIT6 (ORCPT ); Tue, 2 May 2006 04:19:58 -0400 Message-ID: <346557995.03234@ustc.edu.cn> X-EYOUMAIL-SMTPAUTH: wfg@mail.ustc.edu.cn Date: Tue, 2 May 2006 16:20:10 +0800 From: Wu Fengguang To: Jens Axboe Cc: linux-kernel@vger.kernel.org, Linus Torvalds , Andrew Morton , Nick Piggin , Badari Pulavarty Subject: Re: [RFC] kernel facilities for cache prefetching Message-ID: <20060502082009.GA9038@mail.ustc.edu.cn> Mail-Followup-To: Wu Fengguang , Jens Axboe , linux-kernel@vger.kernel.org, Linus Torvalds , Andrew Morton , Nick Piggin , Badari Pulavarty References: <20060502075049.GA5000@mail.ustc.edu.cn> <20060502080935.GS3814@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060502080935.GS3814@suse.de> User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1017 Lines: 20 On Tue, May 02, 2006 at 10:09:36AM +0200, Jens Axboe wrote: > I tried something very similar to this years ago, except I made it > explicit instead of hiding it in the blk_run_backing_dev() which we > didn't have at that time. My initial results showed that you would get a > load of requests for different pages so would end up doing io randomly > instead again. Yes, the hard one would be _not_ to impact normal I/Os in any way. A simple solution for the case of deadline scheduler would be: - static const int read_expire = HZ / 2; /* max time before a read is submitted. */ + static const int read_expire = HZ / 2; /* max time before a impending read is submitted. */ + static const int reada_expire = HZ * 30; /* max time before a read-ahead is submitted. */ Wu - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/