linux-kernel - Re: [RFC PATCH 2/2] mm/vmscan.c: Prevent allocating shrinker

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Message-ID: <Ya80MSTbKmsTfXjf@dhcp22.suse.cz>
Date:   Tue, 7 Dec 2021 11:15:13 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Yang Shi <shy828301@...il.com>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Nico Pache <npache@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Roman Gushchin <guro@...com>,
        Vladimir Davydov <vdavydov.dev@...il.com>, raquini@...hat.com
Subject: Re: [RFC PATCH 2/2] mm/vmscan.c: Prevent allocating shrinker_info on
 offlined nodes

On Mon 06-12-21 10:26:32, Yang Shi wrote:
[...]
> But IMHO actually the memory usage should be not that bad for memcg
> heavy usecases since there should be not too many "never onlined"
> nodes for such workloads?

Hardware with very sparse nodes topology are really scarce. More likely
on ppc (LPARs) but even then we are talking about really low number of
nodes. At least this is my experience.

So while the memory wasting is possible it doesn't seem to be a really
pressing problem. I would be more careful about a code which scales with
MAX_NUMNODES because that can be really large.
-- 
Michal Hocko
SUSE Labs