Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761134AbXESGdU (ORCPT ); Sat, 19 May 2007 02:33:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755123AbXESGdO (ORCPT ); Sat, 19 May 2007 02:33:14 -0400 Received: from smtp2.linux-foundation.org ([207.189.120.14]:46370 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755094AbXESGdN (ORCPT ); Sat, 19 May 2007 02:33:13 -0400 Date: Fri, 18 May 2007 23:28:24 -0700 From: Andrew Morton To: Fengguang Wu Cc: linux-kernel@vger.kernel.org, Andi Kleen , Jens Axboe , Oleg Nesterov , Steven Pratt , Ram Pai Subject: Re: [PATCH 1/9] readahead: introduce PG_readahead Message-Id: <20070518232824.9917d794.akpm@linux-foundation.org> In-Reply-To: <379355695.83536@ustc.edu.cn> References: <20070516224752.500812933@mail.ustc.edu.cn> <379355695.83536@ustc.edu.cn> X-Mailer: Sylpheed 2.4.1 (GTK+ 2.8.17; x86_64-unknown-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 Content-Length: 795 Lines: 18 On Thu, 17 May 2007 06:47:53 +0800 Fengguang Wu wrote: > Introduce a new page flag: PG_readahead. Is there any way in which we can avoid adding a new page flag? We have the advantage that if the kernel very occasionally gets the wrong result for PageReadahead(page), nothing particularly bad will happen, so we can do racy things. >From a quick peek, it appears that PG_readahead is only ever set against non-uptodate pages. If true we could perhaps exploit that: say, PageReadahead(page) == PG_referenced && !PG_uptodate? - 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/