linux-kernel - Re: [PATCH v3] mm: memory: fix /proc/meminfo reporting for MLOCK

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Message-ID: <20190917101519.GD1872@dhcp22.suse.cz>
Date:   Tue, 17 Sep 2019 12:15:19 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Lucian Adrian Grijincu <lucian@...com>, linux-mm@...ck.org,
        Souptick Joarder <jrdr.linux@...il.com>,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...com>, Roman Gushchin <guro@...com>
Subject: Re: [PATCH v3] mm: memory: fix /proc/meminfo reporting for
 MLOCK_ONFAULT

On Mon 16-09-19 18:26:19, Kirill A. Shutemov wrote:
> On Fri, Sep 13, 2019 at 02:11:19PM -0700, Lucian Adrian Grijincu wrote:
> > As pages are faulted in MLOCK_ONFAULT correctly updates
> > /proc/self/smaps, but doesn't update /proc/meminfo's Mlocked field.
> 
> I don't think there's something wrong with this behaviour. It is okay to
> keep the page an evictable LRU list (and not account it to NR_MLOCKED).

evictable list is an implementation detail. Having an overview about an
amount of mlocked pages can be important. Lazy accounting makes this
more fuzzy and harder for admins to monitor.

Sure it is not a bug to panic about but it certainly makes life of poor
admins harder.

If there is a pathological THP behavior possible then we should look
into that as well.
-- 
Michal Hocko
SUSE Labs