On Mon, 29 Nov 2021, Rustam Kovhaev wrote: > > I'm not sure that helps. > > The header can't share a cache line with the previous item (because it > > might be mapped for DMA) so will always take a full cache line. > > I thought that DMA API allocates buffers that are larger than page size. > DMA pool seems to be able to give out smaller buffers, but underneath it > seems to be calling page allocator. > The SLOB objects that have this header are all less than page size, and > they cannot end up in DMA code paths, or can they? kmalloc slab allocations must return dmaable memory. If the underlying hardware can only dma to a cache line border then all objects must be aligned that way.
