Re: [PATCH drm-misc-next 2/3] drm/gpuva_mgr: generalize dma_resv/extobj handling and GEM validation

From: Christian König
Date: Wed Oct 11 2023 - 03:09:27 EST


Am 10.10.23 um 22:23 schrieb Dave Airlie:
I think we're then optimizing for different scenarios. Our compute
driver will use mostly external objects only, and if shared, I don't
forsee them bound to many VMs. What saves us currently here is that in
compute mode we only really traverse the extobj list after a preempt
fence wait, or when a vm is using a new context for the first time. So
vm's extobj list is pretty large. Each bo's vma list will typically be
pretty small.
Can I ask why we are optimising for this userspace, this seems
incredibly broken.

We've has this sort of problem in the past with Intel letting the tail
wag the horse, does anyone remember optimising relocations for a
userspace that didn't actually need to use relocations?

We need to ask why this userspace is doing this, can we get some
pointers to it? compute driver should have no reason to use mostly
external objects, the OpenCL and level0 APIs should be good enough to
figure this out.

Well that is pretty normal use case, AMD works the same way.

In a multi GPU compute stack you have mostly all the data shared between different hardware devices.

As I said before looking at just the Vulcan use case is not a good idea at all.

Christian.


Dave.