linux-kernel - Re: [PATCH] memcg: add hierarchical effective limits for v2

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Message-ID: <bg5bq2jakwamok6phasdzyn7uckq6cno2asm3mgwxwbes6odae@vu3ngtcibqpo>
Date: Tue, 11 Feb 2025 17:08:03 -0800
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Johannes Weiner <hannes@...xchg.org>, 
	Michal Koutný <mkoutny@...e.com>, "T.J. Mercier" <tjmercier@...gle.com>, Tejun Heo <tj@...nel.org>, 
	Michal Hocko <mhocko@...nel.org>, Muchun Song <muchun.song@...ux.dev>, linux-mm@...ck.org, 
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH] memcg: add hierarchical effective limits for v2

On Tue, Feb 11, 2025 at 04:55:33AM +0000, Roman Gushchin wrote:
[...]
> 
> Maybe I'm missing something, but somehow it wasn't a problem for many years.
> Nothing really changed here.
> 
> So maybe someone can come up with a better explanation of a specific problem
> we're trying to solve here?

The most simple explanation is visibility. Workloads that used to run
solo are being moved to a multi-tenant but non-overcommited environment
and they need to know their capacity which they used to get from system
metrics. Now they have to get from cgroup limit files but usage of
cgroup namespace limits those workloads to extract the needed
information.