Hi KyongHo, On Thu, Sep 8, 2011 at 3:51 PM, KyongHo Cho <pullip.cho@xxxxxxxxxxx> wrote: > 16MB page is less practical in Linux because Linux kernel is unable > to allocated larger physically contiguous memory than 4MB by default. > But I also think that it is needed to support 16MB mapping for IO > virtualization someday Actually we need physically contiguous memory regions that are much bigger (in the tens of megs), so we do utilize 16MB pages. Today we reserve that memory on boot, but the plan is to move to CMA. > Actually, I think your idea is good and does not cause performance degradation. > But I wondered if it is really useful. Well, the alternative is to duplicate this logic in every IOMMU driver. Go ahead and try to rebase your driver on my recent patch set and see if you like it; the result should significantly simplify your map/unmap functions. You only need to add this line: static unsigned long s5p_iommu_pgsizes = SZ_4K | SZ_64K | SZ_1M | SZ_16M; and then advertise it with iommu_register, and you're done. The IOMMU core will only ask you to handle a single page from now on, and will take care of the rest. > The caller of iommu_map() gives gfp_order that is the size of the physical > memory to map. I've changed it in the patch :) This way users are not bound to rigid mapping sizes (this allows us to better utilize the physically-contiguous memory region we reserve on boot). Thanks, Ohad. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
