On Tue, Oct 30, 2018 at 09:39:24AM -0300, Ard Biesheuvel wrote: > (add back the list)
Oi! Go back on holiday! > On 30 October 2018 at 09:07, Cohen, Eugene <[email protected]> wrote: > > Has this patch been tested on a system that does not have coherent DMA? > > > > It's not clear that this change would actually be faster on a system of that > > type since using common buffers imply access to uncached memory. Depending > > on the access patterns the uncached memory access could be more time > > consuming than cache maintenance operations. > > I haven't had time to look at these patches yet. > > I agree with Eugene's concern: the directional DMA routines are much > more performant on implementations with non-coherent DMA, and so > common buffers should be avoided unless we are dealing with data > structures that are truly shared between the CPU and the device. > > Since this is obviously not the case here, could we please have some > numbers about the performance improvement we are talking about here? > Would it be possible to improve the IOMMU handling code instead? On an unrelated note to the concerns above: Why has a fundamental change to the behaviour of one of the industry standard drivers been pushed at the very end of the stable cycle? Regards, Leif _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
