Quoting Lucas Stach (2017-11-30 17:34:28) > Dma-bufs should already be device coherent, as they are only pulled in the > CPU domain via the begin/end cpu_access calls. As we cache the mapping set > up by dma_map_sg a CPU sync at this point will not actually guarantee proper > coherency on non-coherent architectures, so we can as well stop pretending.
That matches my understanding of the dma-buf API, device coherent with explicit cpu coherency managed by ioctl. > This is an important performance fix for architectures which need explicit > cache synchronization and userspace doing lots of dma-buf imports. > Improves Weston on Etnaviv performance 5x, where before this patch > 90% > of Weston CPU time was spent synchronizing caches for buffers which are > already device coherent. > > Signed-off-by: Lucas Stach <l.st...@pengutronix.de> Sent an equivalent patch through i915's CI, which didn't show any problems. Reviewed-by: Chris Wilson <ch...@chris-wilson.co.uk> -Chris _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
