On Thu, Jun 27, 2019 at 2:11 AM Daniel Vetter <daniel@xxxxxxxx> wrote: > I feel like a better approach would by to add a cgroup for the various > engines on the gpu, and then also account all the sdma (or whatever the > name of the amd copy engines is again) usage by ttm_bo moves to the right > cgroup. I think that's a more meaningful limitation. For direct thrashing > control I think there's both not enough information available in the > kernel (you'd need some performance counters to watch how much bandwidth > userspace batches/CS are wasting), and I don't think the ttm eviction > logic is ready to step over all the priority inversion issues this will > bring up. Managing sdma usage otoh will be a lot more straightforward (but > still has all the priority inversion problems, but in the scheduler that > might be easier to fix perhaps with the explicit dependency graph - in the > i915 scheduler we already have priority boosting afaiui). My concern with hooking into the engine/ lower level is that the engine may not be process/cgroup aware. So the bandwidth tracking is per device. I am also wondering if this is also potentially be a case of perfect getting in the way of good. While ttm_bo_handle_move_mem may not track everything, it is still a key function for a lot of the memory operation. Also, if the programming model is designed to bypass the kernel then I am not sure if there are anything the kernel can do. (Things like kernel-bypass network stack comes to mind.) All that said, I will certainly dig deeper into the topic. Regards, Kenny
