linux-kernel - Re: [RFC v1] memcg: add memcg lru for page reclaiming

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>] [day] [month] [year] [list]

Message-ID: <20191023080823.GH754@dhcp22.suse.cz>
Date:   Wed, 23 Oct 2019 10:08:23 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Hillf Danton <hdanton@...a.com>
Cc:     linux-mm <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Chris Down <chris@...isdown.name>, Tejun Heo <tj@...nel.org>,
        Roman Gushchin <guro@...com>,
        Johannes Weiner <hannes@...xchg.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Minchan Kim <minchan@...nel.org>, Mel Gorman <mgorman@...e.de>
Subject: Re: [RFC v1] memcg: add memcg lru for page reclaiming

On Wed 23-10-19 12:44:48, Hillf Danton wrote:
> 
> On Tue, 22 Oct 2019 15:58:32 +0200 Michal Hocko wrote:
> > 
> > On Tue 22-10-19 21:30:50, Hillf Danton wrote:
[...]
> > > in this RFC after ripping pages off
> > > the first victim, the work finishes with the first ancestor of the victim
> > > added to lru.
> > > 
> > > Recaliming is defered until kswapd becomes active.
> > 
> > This is a wrong assumption because high limit might be configured way
> > before kswapd is woken up.
> 
> This change was introduced because high limit breach looks not like a
> serious problem in the absence of memory pressure. Lets do the hard work,
> reclaiming one memcg a time up through the hierarchy, when kswapd becomes
> active. It also explains the BH introduced.

But this goes against the main motivation for the high limit - to
throttle. It is not all that important that there is not global memory
pressure. The preventive high limit reclaim is there to make sure that
the specific memcg is kept in a reasonable containment.
-- 
Michal Hocko
SUSE Labs