Messages in this thread | | | Date | Tue, 30 Nov 2021 10:41:15 +0100 (CET) | From | Christoph Lameter <> | Subject | Re: [PATCH v4] slob: add size header to all allocations |
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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.
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