On Thu, Sep 04, 2014 at 09:44:04AM +0200, Thomas Hellstrom wrote: > Last time I tested, (and it seems like Michel is on the same track), > writing with the CPU to write-combined memory was substantially faster > than writing to cached memory, with the additional side-effect that CPU > caches are left unpolluted. > > Moreover (although only tested on Intel's embedded chipsets), texturing > from cpu-cache-coherent PCI memory was a real GPU performance hog > compared to texturing from non-snooped memory. Hence, whenever a buffer > could be classified as GPU-read-only (or almost at least), it should be > placed in write-combined memory. Just a quick comment since this explicitly referes to intel chips: On desktop/laptop chips with the big shared l3/l4 caches it's the other way round. Cached uploads are substantially faster than wc and not using coherent access is a severe perf hit for texturing. I guess the hw guys worked really hard to hide the snooping costs so that the gpu can benefit from the massive bandwidth these caches can provide. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
