On 4/19/2023 6:06 PM, Catalin Marinas wrote: > On Thu, Mar 16, 2023 at 11:38:47AM -0700, Isaac Manjarres wrote: >[...]>> Given this, I don't think there's anything blocking this series from >> being merged. The requirement for SWIOTLB to get to the minimum >> kmalloc alignment down to 8 bytes shouldn't prevent this series from >> being merged, as the amount of memory that is allocated for SWIOTLB >> can be configured through the commandline to minimize the impact of >> having SWIOTLB memory. Additionally, even if no SWIOTLB is present, >> this series still offers memory savings on a lot of ARM64 platforms >> by using the cache line size as the minimum alignment for kmalloc. > > Actually, there's some progress on the swiotlb front to allow dynamic > allocation. I haven't reviewed the series yet (I wasn't aware of it > until v2) but at a quick look, it limits the dynamic allocation to > bouncing buffers of at least a page size. Maybe this can be later > improved for buffers below ARCH_DMA_MINALIGN. Indeed. My patch allocates dynamic bounce buffers with dma_direct_alloc_pages() to keep things simple for now, but there is no real reason against allocating less than a page with another suitable allocator. However, I'd be interested what the use case is, so I can assess the performance impact, which depends on workload, and FYI it may not even be negative. ;-) Petr Tesarik
