linux-kernel - Re: memcg reclaim demotion wrt. isolation

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

Message-ID: <Y5mcLdBioMG+G9WS@dhcp22.suse.cz>
Date:   Wed, 14 Dec 2022 10:49:33 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Yang Shi <shy828301@...il.com>, Wei Xu <weixugc@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Feng Tang <feng.tang@...el.com>
Subject: Re: memcg reclaim demotion wrt. isolation

On Wed 14-12-22 10:57:52, Huang, Ying wrote:
> Michal Hocko <mhocko@...e.com> writes:
[...]
> > This makes sense but I suspect that this wasn't intended also for
> > memcg triggered reclaim. This would mean that a memory pressure in one
> > hierarchy could trigger paging out pages of a different hierarchy if the
> > demotion target is close to full.
> 
> It seems that it's unnecessary to wake up kswapd of demotion target node
> in most cases.  Because we will try to reclaim on the demotion target
> nodes in the loop of do_try_to_free_pages().  It may be better to loop
> the zonelist in the reverse order.  Because the demotion targets are
> usually located at the latter of the zonelist.

Reclaiming from demotion targets first would deal with that as well.
Thanks! Let's establish whether this is something we really need/want
fix first.
-- 
Michal Hocko
SUSE Labs