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

[David Hildenbrand <david@redhat.com>]

On 19.08.25 13:49, Maarten Lankhorst wrote:
> When exporting dma-bufs to other devices, even when it is allowed to use
> move_notify in some drivers, performance will degrade severely when
> eviction happens.
> 
> A perticular example where this can happen is in a multi-card setup,
> where PCI-E peer-to-peer is used to prevent using access to system memory.
> 
> If the buffer is evicted to system memory, not only the evicting GPU wher
> the buffer resided is affected, but it will also stall the GPU that is
> waiting on the buffer.
> 
> It also makes sense for long running jobs not to be preempted by having
> its buffers evicted, so it will make sense to have the ability to pin
> from system memory too.
> 
> This is dependant on patches by Dave Airlie, so it's not part of this
> series yet. But I'm planning on extending pinning to the memory cgroup
> controller in the future to handle this case.
> 
> 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.
> 
> 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.

The term "pinning" is overloaded, and frequently we refer to 
pin_user_pages() and friends.

So I'm wondering if there is an alternative term to describe what you 
want to achieve.

Is it something like "unevictable" ?

-- 
Cheers

David / dhildenb