From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752777AbZHSN2g (ORCPT ); Wed, 19 Aug 2009 09:28:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752304AbZHSN2g (ORCPT ); Wed, 19 Aug 2009 09:28:36 -0400 Received: from mail-gx0-f205.google.com ([209.85.217.205]:37493 "EHLO mail-gx0-f205.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752012AbZHSN2d convert rfc822-to-8bit (ORCPT ); Wed, 19 Aug 2009 09:28:33 -0400 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=otYnfI0mt/5eOtybtgC5Te0a8FVmaztpMHBBBraEMbLHp2Kx/8iCHOY/NPtfjLwqjw otLUbl7TshzELrCjsn29mEeVFgSqmt3zwETaRaO8kpejfASt3LGUFusawSiCsM5mimX4 yjm1Fl5S/ootKge7kcanxiWrYY2oq8dy/qB9g= MIME-Version: 1.0 In-Reply-To: <2f11576a0908190619t9951959o3841091e51324c8@mail.gmail.com> References: <20090816051502.GB13740@localhost> <20090816112910.GA3208@localhost> <20090818234310.A64B.A69D9226@jp.fujitsu.com> <20090819120117.GB7306@localhost> <2f11576a0908190505h6da96280xf67c962aa3f5ba07@mail.gmail.com> <20090819121017.GA8226@localhost> <28c262360908190525i6e56ead0mb8dcb01c3d1a69f1@mail.gmail.com> <2f11576a0908190619t9951959o3841091e51324c8@mail.gmail.com> Date: Wed, 19 Aug 2009 22:28:33 +0900 Message-ID: <28c262360908190628i3f323714kf011f9b0fd4cd15@mail.gmail.com> Subject: Re: [RFC] respect the referenced bit of KVM guest pages? From: Minchan Kim To: KOSAKI Motohiro Cc: Wu Fengguang , Rik van Riel , Jeff Dike , Avi Kivity , Andrea Arcangeli , "Yu, Wilfred" , "Kleen, Andi" , Hugh Dickins , Andrew Morton , Christoph Lameter , Mel Gorman , LKML , linux-mm Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 19, 2009 at 10:19 PM, KOSAKI Motohiro wrote: > 2009/8/19 Minchan Kim : >> On Wed, Aug 19, 2009 at 9:10 PM, Wu Fengguang wrote: >>> On Wed, Aug 19, 2009 at 08:05:19PM +0800, KOSAKI Motohiro wrote: >>>> >> page_referenced_file? >>>> >> I think we should change page_referenced(). >>>> > >>>> > Yeah, good catch. >>>> > >>>> >> >>>> >> Instead, How about this? >>>> >> ============================================== >>>> >> >>>> >> Subject: [PATCH] mm: stop circulating of referenced mlocked pages >>>> >> >>>> >> Currently, mlock() systemcall doesn't gurantee to mark the page PG_Mlocked >>>> > >>>> >                                                    mark PG_mlocked >>>> > >>>> >> because some race prevent page grabbing. >>>> >> In that case, instead vmscan move the page to unevictable lru. >>>> >> >>>> >> However, Recently Wu Fengguang pointed out current vmscan logic isn't so >>>> >> efficient. >>>> >> mlocked page can move circulatly active and inactive list because >>>> >> vmscan check the page is referenced _before_ cull mlocked page. >>>> >> >>>> >> Plus, vmscan should mark PG_Mlocked when cull mlocked page. >>>> > >>>> >                           PG_mlocked >>>> > >>>> >> Otherwise vm stastics show strange number. >>>> >> >>>> >> This patch does that. >>>> > >>>> > Reviewed-by: Wu Fengguang >>>> >>>> Thanks. >>>> >>>> >>>> >>>> >> Index: b/mm/rmap.c >>>> >> =================================================================== >>>> >> --- a/mm/rmap.c       2009-08-18 19:48:14.000000000 +0900 >>>> >> +++ b/mm/rmap.c       2009-08-18 23:47:34.000000000 +0900 >>>> >> @@ -362,7 +362,9 @@ static int page_referenced_one(struct pa >>>> >>        * unevictable list. >>>> >>        */ >>>> >>       if (vma->vm_flags & VM_LOCKED) { >>>> >> -             *mapcount = 1;  /* break early from loop */ >>>> >> +             *mapcount = 1;          /* break early from loop */ >>>> >> +             *vm_flags |= VM_LOCKED; /* for prevent to move active list */ >>>> > >>>> >> +             try_set_page_mlocked(vma, page); >>>> > >>>> > That call is not absolutely necessary? >>>> >>>> Why? I haven't catch your point. >>> >>> Because we'll eventually hit another try_set_page_mlocked() when >>> trying to unmap the page. Ie. duplicated with another call you added >>> in this patch. > > Correct. > > >> Yes. we don't have to call it and we can make patch simple. >> I already sent patch on yesterday. >> >> http://marc.info/?l=linux-mm&m=125059325722370&w=2 >> >> I think It's more simple than KOSAKI's idea. >> Is any problem in my patch ? > > Hmm, I think > > 1. Anyway, we need turn on PG_mlock. I add my patch again to explain. diff --git a/mm/rmap.c b/mm/rmap.c index ed63894..283266c 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -358,6 +358,7 @@ static int page_referenced_one(struct page *page, */ if (vma->vm_flags & VM_LOCKED) { *mapcount = 1; /* break early from loop */ + *vm_flags |= VM_LOCKED; goto out_unmap; } diff --git a/mm/vmscan.c b/mm/vmscan.c index d224b28..d156e1d 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -632,7 +632,8 @@ static unsigned long shrink_page_list(struct list_head *page_list, sc->mem_cgroup, &vm_flags); /* In active use or really unfreeable? Activate it. */ if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && - referenced && page_mapping_inuse(page)) + referenced && page_mapping_inuse(page) + && !(vm_flags & VM_LOCKED)) goto activate_locked; By this check, the page can be reached at try_to_unmap after page_referenced in shrink_page_list. At that time PG_mlocked will be set. > 2. PG_mlock prevent livelock because page_evictable() check is called > at very early in shrink_page_list(). -- Kind regards, Minchan Kim