linux-kernel - Re: [PATCH] mm: vmpressure: don't count userspace-induced reclaim as memory pressure

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: <YrSWruhPlJV1X9kp@dhcp22.suse.cz>
Date:   Thu, 23 Jun 2022 18:37:02 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Yosry Ahmed <yosryahmed@...gle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>, NeilBrown <neilb@...e.de>,
        Alistair Popple <apopple@...dia.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Peter Xu <peterx@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Cgroups <cgroups@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: vmpressure: don't count userspace-induced reclaim as
 memory pressure

On Thu 23-06-22 09:22:35, Yosry Ahmed wrote:
> On Thu, Jun 23, 2022 at 2:43 AM Michal Hocko <mhocko@...e.com> wrote:
> >
> > On Thu 23-06-22 01:35:59, Yosry Ahmed wrote:
[...]
> > > In our internal version of memory.reclaim that we recently upstreamed,
> > > we do not account vmpressure during proactive reclaim (similar to how
> > > psi is handled upstream). We want to make sure this behavior also
> > > exists in the upstream version so that consolidating them does not
> > > break our users who rely on vmpressure and will start seeing increased
> > > pressure due to proactive reclaim.
> >
> > These are good reasons to have this patch in your tree. But why is this
> > patch benefitial for the upstream kernel? It clearly adds some code and
> > some special casing which will add a maintenance overhead.
> 
> It is not just Google, any existing vmpressure users will start seeing
> false pressure notifications with memory.reclaim. The main goal of the
> patch is to make sure memory.reclaim does not break pre-existing users
> of vmpressure, and doing it in a way that is consistent with psi makes
> sense.

memory.reclaim is v2 only feature which doesn't have vmpressure
interface. So I do not see how pre-existing users of the upstream kernel
can see any breakage.

-- 
Michal Hocko
SUSE Labs