From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754411Ab2A0FPZ (ORCPT ); Fri, 27 Jan 2012 00:15:25 -0500 Received: from acsinet15.oracle.com ([141.146.126.227]:31966 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751736Ab2A0FPY convert rfc822-to-8bit (ORCPT ); Fri, 27 Jan 2012 00:15:24 -0500 MIME-Version: 1.0 Message-ID: <22f6781b-9cc4-4857-b3e1-e2d9f595f64d@default> Date: Thu, 26 Jan 2012 21:15:16 -0800 (PST) From: Dan Magenheimer To: Rik van Riel Cc: Andrew Morton , Dave Hansen , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Konrad Wilk , Seth Jennings , Nitin Gupta , Nebojsa Trpkovic , minchan@kernel.org, KAMEZAWA Hiroyuki , Chris Mason Subject: RE: [PATCH] mm: implement WasActive page flag (for improving cleancache) References: <4F218D36.2060308@linux.vnet.ibm.com> <9fcd06f5-360e-4542-9fbb-f8c7efb28cb6@default> <20120126163150.31a8688f.akpm@linux-foundation.org> <20120126171548.2c85dd44.akpm@linux-foundation.org> <7198bfb3-1e32-40d3-8601-d88aed7aabd8@default> <4F221AFE.6070108@redhat.com> In-Reply-To: <4F221AFE.6070108@redhat.com> X-Priority: 3 X-Mailer: Oracle Beehive Extensions for Outlook 2.0.1.6 (510070) [OL 12.0.6607.1000 (x86)] Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-Source-IP: acsinet21.oracle.com [141.146.126.237] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090201.4F2232DF.0094,ss=1,re=0.000,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Rik van Riel [mailto:riel@redhat.com] > Subject: Re: [PATCH] mm: implement WasActive page flag (for improving cleancache) > > On 01/26/2012 09:43 PM, Dan Magenheimer wrote: > > > Maybe the Active page bit could be overloaded with some minor > > rewriting? IOW, perhaps the Active bit could be ignored when > > the page is moved to the inactive LRU? (Confusing I know, but I am > > just brainstorming...) > > The PG_referenced bit is already overloaded. We keep > the bit set when we move a page from the active to the > inactive list, so a page that was previously active > only needs to be referenced once to become active again. > > The LRU bits (PG_lru, PG_active, etc) are needed to > figure out which LRU list the page is on. I don't > think we can overload those... I suspected that was true, but was just brainstorming. Thanks for confirming. Are there any other page bits that are dont-care when a page is on an LRU list? I'd also be interested in your/RedHat's opinion on the 64-bit vs 32-bit market. Will RHEL7 even support 32-bit? Dan