netdev - Re: [PATCH v4] memcg: expose socket memory pressure in a cgroup

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Message-ID: <aJzTeyRTu_sfm-9R@slm.duckdns.org>
Date: Wed, 13 Aug 2025 08:03:39 -1000
From: Tejun Heo <tj@...nel.org>
To: Michal Koutný <mkoutny@...e.com>
Cc: 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>,
	Kuniyuki Iwashima <kuniyu@...gle.com>,
	David Ahern <dsahern@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	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 v4] memcg: expose socket memory pressure in a cgroup

Hello,

On Wed, Aug 13, 2025 at 02:03:28PM +0200, Michal Koutný wrote:
...
> One more point to clarify -- should the value include throttling from
> ancestors or not. (I think both are fine but) this semantic should also
> be described in the docs. I.e. current proposal is
> 	value = sum_children + self
> and if you're see that C's value is 0, it doesn't mean its sockets
> weren't subject of throttling. It just means you need to check also
> values in C ancestors. Does that work?

I was more thinking that it would account for all throttled durations, but
it's true that we only count locally originating events for e.g.
memory.events::low or pids.events::max. Hmm... I'm unsure. So, for events, I
think local sources make sense as it's tracking what limits are triggering
where. However, I'm not sure that translates well to throttle duration which
is closer to pressure metrics than event counters. We don't distinguish the
sources of contention when presenting pressure metrics after all.

Thanks.

-- 
tejun