From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750819AbVI0DGM (ORCPT ); Mon, 26 Sep 2005 23:06:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750824AbVI0DGM (ORCPT ); Mon, 26 Sep 2005 23:06:12 -0400 Received: from xenotime.net ([66.160.160.81]:17595 "HELO xenotime.net") by vger.kernel.org with SMTP id S1750819AbVI0DGL (ORCPT ); Mon, 26 Sep 2005 23:06:11 -0400 Date: Mon, 26 Sep 2005 20:06:08 -0700 From: "Randy.Dunlap" To: Alan Stern Cc: linux-kernel@vger.kernel.org Subject: Re: Readahead Message-Id: <20050926200608.7fe0ff89.rdunlap@xenotime.net> In-Reply-To: References: Organization: YPO4 X-Mailer: Sylpheed version 1.0.5 (GTK+ 1.2.10; i686-pc-linux-gnu) 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 On Mon, 26 Sep 2005 22:38:21 -0400 (EDT) Alan Stern wrote: > Can somebody please tell me where the code is that performs optimistic > readahead when a process does sequential reads on a block device? There's filesystem readahead in fs/buffer.c (__breadahead()), although I don't see any actual callers of it. However, I'm guessing that you are actually thinking about the anticipatory IO scheduler (as), which is found in drivers/block/as-iosched.c. drivers/block/ll_rw_blk.c also does some readahead (READA) work. > And can someone explain why those readahead calls are allowed to extend > beyond the end of the device? Nope. --- ~Randy