From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 9E0576B004D for ; Wed, 19 Aug 2009 09:19:42 -0400 (EDT) Received: by gxk12 with SMTP id 12so6043703gxk.4 for ; Wed, 19 Aug 2009 06:19:46 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <28c262360908190525i6e56ead0mb8dcb01c3d1a69f1@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> Date: Wed, 19 Aug 2009 22:19:46 +0900 Message-ID: <2f11576a0908190619t9951959o3841091e51324c8@mail.gmail.com> Subject: Re: [RFC] respect the referenced bit of KVM guest pages? From: KOSAKI Motohiro Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: Minchan Kim 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 List-ID: 2009/8/19 Minchan Kim : > On Wed, Aug 19, 2009 at 9:10 PM, Wu Fengguang wro= te: >> 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? >>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>> >> >>> >> Subject: [PATCH] mm: stop circulating of referenced mlocked pages >>> >> >>> >> Currently, mlock() systemcall doesn't gurantee to mark the page PG_M= locked >>> > >>> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0mark 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. >>> > >>> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 PG_mlocked >>> > >>> >> Otherwise vm stastics show strange number. >>> >> >>> >> This patch does that. >>> > >>> > Reviewed-by: Wu Fengguang >>> >>> Thanks. >>> >>> >>> >>> >> Index: b/mm/rmap.c >>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>> >> --- a/mm/rmap.c =A0 =A0 =A0 2009-08-18 19:48:14.000000000 +0900 >>> >> +++ b/mm/rmap.c =A0 =A0 =A0 2009-08-18 23:47:34.000000000 +0900 >>> >> @@ -362,7 +362,9 @@ static int page_referenced_one(struct pa >>> >> =A0 =A0 =A0 =A0* unevictable list. >>> >> =A0 =A0 =A0 =A0*/ >>> >> =A0 =A0 =A0 if (vma->vm_flags & VM_LOCKED) { >>> >> - =A0 =A0 =A0 =A0 =A0 =A0 *mapcount =3D 1; =A0/* break early from lo= op */ >>> >> + =A0 =A0 =A0 =A0 =A0 =A0 *mapcount =3D 1; =A0 =A0 =A0 =A0 =A0/* bre= ak early from loop */ >>> >> + =A0 =A0 =A0 =A0 =A0 =A0 *vm_flags |=3D VM_LOCKED; /* for prevent t= o move active list */ >>> > >>> >> + =A0 =A0 =A0 =A0 =A0 =A0 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=3Dlinux-mm&m=3D125059325722370&w=3D2 > > 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. 2. PG_mlock prevent livelock because page_evictable() check is called at very early in shrink_page_list(). -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org