Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 19 May 2022 09:39:57 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     CGEL <cgel.zte@gmail.com>
Cc:     Balbir Singh <bsingharora@gmail.com>, akpm@linux-foundation.org,
        ammarfaizi2@gnuweeb.org, oleksandr@natalenko.name,
        willy@infradead.org, linux-mm@kvack.org, corbet@lwn.net,
        linux-kernel@vger.kernel.org, xu xin <xu.xin16@zte.com.cn>,
        Yang Yang <yang.yang29@zte.com.cn>,
        Ran Xiaokai <ran.xiaokai@zte.com.cn>,
        wangyong <wang.yong12@zte.com.cn>,
        Yunkai Zhang <zhang.yunkai@zte.com.cn>,
        Jiang Xuexin <jiang.xuexin@zte.com.cn>
Subject: Re: [PATCH] mm/ksm: introduce ksm_enabled for each processg
Message-ID: <YoX0TWoNw3HqH/X/@dhcp22.suse.cz>
References: <20220517092701.1662641-1-xu.xin16@zte.com.cn>
 <YoSZE7Iak3AYA4VE@balbir-desktop>
 <6284a2ef.1c69fb81.e53cd.32b2@mx.google.com>
 <YoTjJH7+QD+DSrW8@dhcp22.suse.cz>
 <6285e519.1c69fb81.4f3fe.8057@mx.google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <6285e519.1c69fb81.4f3fe.8057@mx.google.com>
Precedence: bulk

On Thu 19-05-22 06:35:03, CGEL wrote:
> On Wed, May 18, 2022 at 02:14:28PM +0200, Michal Hocko wrote:
> > On Wed 18-05-22 07:40:30, CGEL wrote:
> > [...]
> > > 2. process_madvise is still a kind of madvise. processs_madvise from
> > > another process overrides the intention of origin app code ifself that
> > > also calls madvise, which is unrecoverable. For example, if a process "A"
> > > which madvises just one part of VMAs (not all) as MERGEABLE run on the OS
> > > already, meanwhile, if another process which doesn't know the information
> > > of "A" 's MERGEABLE areas, then call process_madvise to advise all VMAs of
> > > "A" as MERGEABLE, the original MERGEABLE information of "A" calling madivse
> > > is erasured permanently.
> > 
> > I do not really follow. How is this any different from an external
> > process modifying the process wide policy via the proc or any other
> > interface?
> 
> In this patch, you can see that we didn't modify the flag of any VMA of
> the target process, which is different from process_madvise. So it is
> easy to keep the original MERGEABLE information of the target process
> when we turn back to the default state from the state "always".

This means that /proc/<pid>/smaps doesn't show the real state, right?

-- 
Michal Hocko
SUSE Labs