On Fri, Nov 02, 2018 at 07:35:42AM +0100, Christoph Hellwig wrote: > On Thu, Nov 01, 2018 at 02:07:55PM +0000, Robin Murphy wrote: > > On 31/10/2018 20:03, Nicolin Chen wrote: > >> The addresses within a single page are always contiguous, so it's > >> not so necessary to allocate one single page from CMA area. Since > >> the CMA area has a limited predefined size of space, it might run > >> out of space in some heavy use case, where there might be quite a > >> lot CMA pages being allocated for single pages. > >> > >> This patch tries to skip CMA allocations of single pages and lets > >> them go through normal page allocations. This would save resource > >> in the CMA area for further more CMA allocations. > > > > In general, this seems to make sense to me. It does represent a theoretical > > change in behaviour for devices which have their own CMA area somewhere > > other than kernel memory, and only ever make non-atomic allocations, but > > I'm not sure whether that's a realistic or common enough case to really > > worry about. > > Yes, I think we should make the decision in dma_alloc_from_contiguous > based on having a per-dev CMA area or not. There is a lot of cruft in
It seems that cma_alloc() already has a CMA area check? Would it be duplicated to have a similar one in dma_alloc_from_contiguous? > this area that should be cleaned up while we're at it, like always > falling back to the normal page allocator if there is no CMA area or > nothing suitable found in dma_alloc_from_contiguous instead of > having to duplicate all that in the caller. Am I supposed to clean up things that's mentioned above by moving the fallback allocator into dma_alloc_from_contiguous, or to just move my change (the count check) into dma_alloc_from_contiguous? I understand that'd be great to have a cleanup, yet feel it could be done separately as this patch isn't really a cleanup change. Thanks Nicolin _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
