linux-kernel - Re: [PATCH v2] mm: vmscan: reclaim anon pages if there are swapcache pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJD7tkYivogrRtAx8a+EPfjRqQNgoOZFZyG8rC91E_hW6pdTEw@mail.gmail.com>
Date:   Wed, 23 Aug 2023 08:29:19 -0700
From:   Yosry Ahmed <yosryahmed@...gle.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Liu Shixin <liushixin2@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        wangkefeng.wang@...wei.com, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2] mm: vmscan: reclaim anon pages if there are swapcache pages

On Wed, Aug 23, 2023 at 6:12 AM Michal Hocko <mhocko@...e.com> wrote:
>
> On Wed 23-08-23 10:00:58, Liu Shixin wrote:
> >
> >
> > On 2023/8/23 0:35, Yosry Ahmed wrote:
> > > On Mon, Aug 21, 2023 at 6:54 PM Liu Shixin <liushixin2@...wei.com> wrote:
> > >> When spaces of swap devices are exhausted, only file pages can be reclaimed.
> > >> But there are still some swapcache pages in anon lru list. This can lead
> > >> to a premature out-of-memory.
> > >>
> > >> This problem can be fixed by checking number of swapcache pages in
> > >> can_reclaim_anon_pages(). For memcg v2, there are swapcache stat that can
> > >> be used directly. For memcg v1, use total_swapcache_pages() instead, which
> > >> may not accurate but can solve the problem.
> > > Interesting find. I wonder if we really don't have any handling of
> > > this situation.
> > I have alreadly test this problem and can confirm that it is a real problem.
> > With 9MB swap space and 10MB mem_cgroup limit，when allocate 15MB memory,
> > there is a probability that OOM occurs.
>
> Could you be more specific about the test and the oom report?

I actually couldn't reproduce it using 9MB of zram and a cgroup with a
10MB limit trying to allocate 15MB of tmpfs, no matter how many
repetitions I do.

>
> --
> Michal Hocko
> SUSE Labs