From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755889AbXKGCXx (ORCPT ); Tue, 6 Nov 2007 21:23:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753235AbXKGCXq (ORCPT ); Tue, 6 Nov 2007 21:23:46 -0500 Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:36126 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751140AbXKGCXo (ORCPT ); Tue, 6 Nov 2007 21:23:44 -0500 Date: Tue, 6 Nov 2007 18:23:44 -0800 (PST) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Rik van Riel cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH 3/10] define page_file_cache In-Reply-To: <20071103185516.24832ab0@bree.surriel.com> Message-ID: References: <20071103184229.3f20e2f0@bree.surriel.com> <20071103185516.24832ab0@bree.surriel.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 3 Nov 2007, Rik van Riel wrote: > Define page_file_cache() function to answer the question: > is page backed by a file? Well its not clear what is meant by a file in the first place. By file you mean disk space in contrast to ram based filesystems? I think we could add a flag to the bdi to indicate wheter the backing store is a disk file. In fact you can also deduce if if a device has no writeback capability set in the BDI. > Unfortunately this needs to use a page flag, since the > PG_swapbacked state needs to be preserved all the way > to the point where the page is last removed from the > LRU. Trying to derive the status from other info in > the page resulted in wrong VM statistics in earlier > split VM patchsets. The bdi may avoid that extra flag.