On 28/11/16 09:57 AM, Jason Gunthorpe wrote: >> On PeerDirect, we have some kind of a middle-ground solution for pinning >> GPU memory. We create a non-ODP MR pointing to VRAM but rely on >> user-space and the GPU not to migrate it. If they do, the MR gets >> destroyed immediately. > > That sounds horrible. How can that possibly work? What if the MR is > being used when the GPU decides to migrate? I would not support that > upstream without a lot more explanation.. Yup, this was our experience when playing around with PeerDirect. There was nothing we could do if the GPU decided to invalidate the P2P mapping. It just meant the application would fail or need complicated logic to detect this and redo just about everything. And given that it was a reasonably rare occurrence during development it probably means not a lot of applications will be developed to handle it and most would end up being randomly broken in environments with memory pressure. Logan -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
