netdev - Re: [PATCH v3] memcg: expose socket memory pressure in a cgroup

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Message-ID: <yruvlyxyy6gsrf2hhtyja5hqnxi2fmdqr63twzxpjrxgffov32@l7gqvdxijs5c>
Date: Wed, 23 Jul 2025 10:38:00 +0200
From: Michal Koutný <mkoutny@...e.com>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Daniel Sedlak <daniel.sedlak@...77.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Jonathan Corbet <corbet@....net>, Neal Cardwell <ncardwell@...gle.com>, 
	David Ahern <dsahern@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Yosry Ahmed <yosry.ahmed@...ux.dev>, linux-mm@...ck.org, netdev@...r.kernel.org, 
	Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Muchun Song <muchun.song@...ux.dev>, cgroups@...r.kernel.org, 
	Matyas Hurtik <matyas.hurtik@...77.com>
Subject: Re: [PATCH v3] memcg: expose socket memory pressure in a cgroup

On Tue, Jul 22, 2025 at 01:11:05PM -0700, Shakeel Butt <shakeel.butt@...ux.dev> wrote:
> > > 1 second is the current implementation and it can be more if the memcg
> > > remains in memory pressure. Regarding usefullness I think the periodic
> > > stat collectors (like cadvisor or Google's internal borglet+rumbo) would
> > > be interested in scraping this interface.
> > 
> > I think the cumulative counter suggested above is better at least.
> 
> It is tied to the underlying implementation. If we decide to use, for
> example, PSI in future, what should this interface show?

Actually, if it was exposed as cummulative time under pressure (not
cummulative events), that's quite similar to PSI.

My curiosity is whether this can be useful to some responsive actions
(hence it's worth watching with high frequency or even create
notification events) or rather like post-hoc examination or low
frequency adjustments (reason for cummulative). I.e. what can this
signal to the userspace?

Michal

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