From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner+w=401wt.eu-S1752163AbZHSNTr@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1752163AbZHSNTr (ORCPT <rfc822;w@1wt.eu>);
	Wed, 19 Aug 2009 09:19:47 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751889AbZHSNTq
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Wed, 19 Aug 2009 09:19:46 -0400
Received: from mail-yx0-f175.google.com ([209.85.210.175]:62437 "EHLO
	mail-yx0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751892AbZHSNTq convert rfc822-to-8bit (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 19 Aug 2009 09:19:46 -0400
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=mime-version:sender:in-reply-to:references:date
         :x-google-sender-auth:message-id:subject:from:to:cc:content-type
         :content-transfer-encoding;
        b=NO3Gi7poQhWiccgZRqBrmFqIvkv9kVaE1Uzq2nAjwxaYFw+jfW858qzQoi8UUt6gJU
         lVGlqUiAuVbOMaP4n34wlVWGB/uVPpNltjtovl12S44TK52INIZHGlcoh1goDLYQQvhV
         pyJx1s+XEHSoXEW0HX577728A1F0ZpjvzhT14=
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
X-Google-Sender-Auth: 2753ef48b1996a92
Message-ID: <2f11576a0908190619t9951959o3841091e51324c8@mail.gmail.com>
Subject: Re: [RFC] respect the referenced bit of KVM guest pages?
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Minchan Kim <minchan.kim@gmail.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>, Rik van Riel <riel@redhat.com>,
       Jeff Dike <jdike@addtoit.com>, Avi Kivity <avi@redhat.com>,
       Andrea Arcangeli <aarcange@redhat.com>,
       "Yu, Wilfred" <wilfred.yu@intel.com>,
       "Kleen, Andi" <andi.kleen@intel.com>,
       Hugh Dickins <hugh.dickins@tiscali.co.uk>,
       Andrew Morton <akpm@linux-foundation.org>,
       Christoph Lameter <cl@linux-foundation.org>, Mel Gorman <mel@csn.ul.ie>,
       LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8BIT
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

2009/8/19 Minchan Kim <minchan.kim@gmail.com>:
> On Wed, Aug 19, 2009 at 9:10 PM, Wu Fengguang<fengguang.wu@intel.com> 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 <fengguang.wu@intel.com>
>>>
>>> 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.
2. PG_mlock prevent livelock because page_evictable() check is called
at very early in shrink_page_list().