Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754429Ab0KWXpW (ORCPT ); Tue, 23 Nov 2010 18:45:22 -0500 Received: from mail-iw0-f174.google.com ([209.85.214.174]:64077 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754137Ab0KWXpV convert rfc822-to-8bit (ORCPT ); Tue, 23 Nov 2010 18:45:21 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=iakl2hLpGIkalpQtp52z4l2zKBCbnF1ocpjvZ4LCbvCIZ7cLf7QjKO4QR36M6Ddmm7 npJWqYwLH8OlD9hTbpWVxHSW45u7InOCMYvKXN1TmTXt4NpRTsoH9ocdYniQqqJ5lC2c 8yCAsYfYvGHXivb86cru3DljYI4w/x35yNc6Q= MIME-Version: 1.0 In-Reply-To: <20101123221049.GR19571@csn.ul.ie> References: <20101122141449.9de58a2c.akpm@linux-foundation.org> <20101122210132.be9962c7.akpm@linux-foundation.org> <20101123093859.GE19571@csn.ul.ie> <87k4k49jii.fsf@gmail.com> <20101123145856.GQ19571@csn.ul.ie> <20101123123535.438e9750.akpm@linux-foundation.org> <20101123221049.GR19571@csn.ul.ie> Date: Wed, 24 Nov 2010 08:45:20 +0900 Message-ID: Subject: Re: [RFC 1/2] deactive invalidated pages From: Minchan Kim To: Mel Gorman Cc: Andrew Morton , Ben Gamari , linux-mm , LKML , Peter Zijlstra , Rik van Riel , KOSAKI Motohiro , Johannes Weiner , Nick Piggin Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2848 Lines: 72 On Wed, Nov 24, 2010 at 7:10 AM, Mel Gorman wrote: > On Tue, Nov 23, 2010 at 12:35:35PM -0800, Andrew Morton wrote: >> On Tue, 23 Nov 2010 14:58:56 +0000 >> Mel Gorman wrote: >> >> > On Tue, Nov 23, 2010 at 09:55:49AM -0500, Ben Gamari wrote: >> > > On Tue, 23 Nov 2010 09:38:59 +0000, Mel Gorman wrote: >> > > > > If it's mapped pagecache then the user was being a bit silly (or didn't >> > > > > know that some other process had mapped the file). ?In which case we >> > > > > need to decide what to do - leave the page alone, deactivate it, or >> > > > > half-deactivate it as this patch does. >> > > > > >> > > > >> > > > What are the odds of an fadvise() user having used mincore() in advance >> > > > to determine if the page was in use by another process? I would guess >> > > > "low" so this half-deactivate gives a chance for the page to be promoted >> > > > again as well as a chance for the flusher threads to clean the page if >> > > > it really is to be reclaimed. >> > > > >> > > Do we really want to make the user jump through such hoops as using >> > > mincore() just to get the kernel to handle use-once pages properly? >> > >> > I would think "no" which is why I support half-deactivating pages so they won't >> > have to. >> >> If the page is page_mapped() then we can assume that some other process >> is using it and we leave it alone *altogether*. >> > > Agreed, that makes perfect sense. > >> If the page is dirty or under writeback (and !page_mapped()) then we >> should assume that we should free it asap. ?The PageReclaim() trick >> might help with that. >> > > Again agreed. > >> I just don't see any argument for moving the page to the head of the >> inactive LRU as a matter of policy. ?We can park it there because we >> can't think of anythnig else to do with it, but it's the wrong place >> for it. >> > > Is there a better alternative? One thing that springs to mind is that we are > not exactly tracking very well what effect these policy changes have. The > analysis scripts I have do a reasonable job on tracking reclaim activity > (although only as part of the mmtests tarball, I should split them out as > a standalone tool) but not the impact - namely minor and major faults. I > should sort that out so we can put better reclaim analysis in place. It can help very much. :) Also, I need time since I am so busy. > > -- > Mel Gorman > Part-time Phd Student ? ? ? ? ? ? ? ? ? ? ? ? ?Linux Technology Center > University of Limerick ? ? ? ? ? ? ? ? ? ? ? ? IBM Dublin Software Lab > -- Kind regards, Minchan Kim -- 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/