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
