Re: [PATCH v5 2/6] mm/memcg: Disable threshold event handlers on PREEMPT_RT

[Valentin Schneider <vschneid@redhat.com>]

On 02/03/23 12:24, Michal Hocko wrote:
> On Thu 02-03-23 10:18:31, Valentin Schneider wrote:
>> On 02/03/23 08:45, Michal Hocko wrote:
>> > On Wed 01-03-23 18:23:19, Valentin Schneider wrote:
> [...]
>> >> I want cgroupv1 to die as much as the next person, but in that specific
>> >> situation I kinda need cgroupv1 to behave somewhat sanely on RT with
>> >> threshold events :/
>> >
>> > Could you expand on the usecase?
>> >
>>
>> In this case it's just some middleware leveraging memcontrol cgroups and
>> setting up callbacks for in-cgroup OOM events. This is a supported feature
>> in cgroupv2, so this isn't a problem of cgroupv1 vs cgroupv2 feature
>> parity, but rather one of being in a transitional phase where the
>> middleware itself hasn't fully migrated to using cgroupv2.
>
> How is this related to the RT kernel config? memcg OOM vs any RT
> assumptions do not really get along well AFAICT.
>

Yep. AIUI the tasks actually relying on RT guarantees DTRT (at least
regarding memory allocations, or lack thereof), but other non-RT-reliant
tasks on other CPUs come and go, hence the memcg involvement.

> --
> Michal Hocko
> SUSE Labs