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

[Michal Koutný]

Hello Shakeel.

On Wed, Feb 05, 2025 at 02:20:29PM -0800, Shakeel Butt <shakeel.butt@xxxxxxxxx> wrote:
> Memcg-v1 exposes hierarchical_[memory|memsw]_limit counters in its
> memory.stat file which applications can use to get their effective limit
> which is the minimum of limits of itself and all of its ancestors.

I was fan of equal idea too [1]. The referenced series also tackles
change notifications (to make this complete for apps that really want to
scale based on the actual limit). I ceased to like it when I realized
there can be hierarchies when the effective value cannot be effectively
:) determined [2].

> This is pretty useful in environments where cgroup namespace is used
> and the application does not have access to the full view of the
> cgroup hierarchy. Let's expose effective limits for memcg v2 as well.

Also, the case for this exposition was never strongly built.
Why isn't PSI enough in your case?

Thanks,
Michal

[1] https://lore.kernel.org/r/20240606152232.20253-1-mkoutny@xxxxxxxx
[2] https://lore.kernel.org/r/7chi6d2sdhwdsfihoxqmtmi4lduea3dsgc7xorvonugkm4qz2j@gehs4slutmtg

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