On 7/30/2026 4:11 PM, Pavel Begunkov wrote: >> >> I wonder if it's possible to perform the PRP list page allocations and >> initialization in nvme_dma_buf_io_map() instead of the I/O path. The >> NVMe dma_pools are per-NUMA-node linked lists protected by spinlocks, >> making them significant CPU hotspots. If the dmabuf registration set >> up a contiguous DMA-coherent list of PRP entries for the pages of the >> registered buffer, any command using the dmabuf and requiring at most >> 1 PRP list page (i.e. length <= 2 MB) could just set its PRP list >> pointer to an offset into the dmabuf's PRP list. > > Possible to an extent, predecessor patches tried that, I left it for > later to keep the series simpler. I guess chaining won't work in > general case. > I mentioned this to Kanchan, Anuj and Nitesh before, they were up to > playing with nvme optimisations in general, and since sgl from Anuj > is ready, maybe they already have a prototype somewhere for that. >
Right, I have prototyped the PRP list optimisation before. I will send it once the initial version of this series lands, to avoid adding new review churn while the rest of the series is pretty settled. > -- > Pavel Begunkov
