Hi Barry, Sorry for jumping in so late. On 8/21/20 4:33 AM, Barry Song wrote: > > with per-numa CMA, smmu will get memory from local numa node to save command > queues and page tables. that means dma_unmap latency will be shrunk much.
Since per-node CMA areas for hugetlb was introduced, I have been thinking about the limited number of CMA areas. In most configurations, I believe it is limited to 7. And, IIRC it is not something that can be changed at runtime, you need to reconfig and rebuild to increase the number. In contrast some configs have NODES_SHIFT set to 10. I wasn't too worried because of the limited hugetlb use case. However, this series is adding another user of per-node CMA areas. With more users, should try to sync up number of CMA areas and number of nodes? Or, perhaps I am worrying about nothing? -- Mike Kravetz