Re: [RFC 0/3] cgroups: Add support for pinned device memory

["Michal Koutný" <mkoutny@suse.com>]

[-- Attachment #1: Type: text/plain, Size: 1136 bytes --]

Hello Maarten.

On Tue, Aug 19, 2025 at 01:49:33PM +0200, Maarten Lankhorst <dev@lankhorst.se> wrote:
> Implementation details:
> 
> For each cgroup up until the root cgroup, the 'min' limit is checked
> against currently effectively pinned value. If the value will go above
> 'min', the pinning attempt is rejected.

How is pinning different from setting a 'min' limit (from a user
perspective)?

> 
> Pinned memory is handled slightly different and affects calculating
> effective min/low values. Pinned memory is subtracted from both,
> and needs to be added afterwards when calculating.
> 
> This is because increasing the amount of pinned memory, the amount of
> free min/low memory decreases for all cgroups that are part of the
> hierarchy.

What is supposed to happen with pinned memory after cgroup removal?
I find the page_counter changes little bit complex without understanding
of the difference between min and pinned. Should this be conceptually
similar to memory.stat:unevictable? Or rather mlock(2)? So far neither
of those needed interaction with min/low values (in memcg).

Thanks,
Michal

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 265 bytes --]