linux-kernel - Re: [PATCH] epoll: account epitem and eppoll

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <20171006074814.76t2bo4bfspq7elg@dhcp22.suse.cz>
Date:   Fri, 6 Oct 2017 09:48:14 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Greg Thelen <gthelen@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>, linux-fsdevel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] epoll: account epitem and eppoll_entry to kmemcg

On Thu 05-10-17 10:21:18, Michal Hocko wrote:
> On Wed 04-10-17 12:33:14, Shakeel Butt wrote:
> > >
> > > I am not objecting to the patch I would just like to understand the
> > > runaway case. ep_insert seems to limit the maximum number of watches to
> > > max_user_watches which should be ~4% of lowmem if I am following the
> > > code properly. pwq_cache should be bound by the number of watches as
> > > well, or am I misunderstanding the code?
> > >
> > 
> > You are absolutely right that there is a per-user limit (~4% of total
> > memory if no highmem) on these caches. I think it is too generous
> > particularly in the scenario where jobs of multiple users are running
> > on the system and the administrator is reducing cost by overcomitting
> > the memory. This is unaccounted kernel memory and will not be
> > considered by the oom-killer. I think by accounting it to kmemcg, for
> > systems with kmem accounting enabled, we can provide better isolation
> > between jobs of different users.
> 
> Thanks for the clarification. For some reason I didn't figure that the
> limit is per user, even though the name suggests so.

Completely forgot to add
Acked-by: Michal Hocko <mhocko@...e.com>
-- 
Michal Hocko
SUSE Labs