Quoting Kenneth Graunke (2017-07-12 08:22:23)
> From: Chris Wilson <[email protected]>
> +static void *
> brw_bo_map_gtt(struct brw_context *brw, struct brw_bo *bo, unsigned flags)
> {
> struct brw_bufmgr *bufmgr = bo->bufmgr;
> @@ -824,10 +831,30 @@ brw_bo_map(struct brw_context *brw, struct brw_bo *bo,
> unsigned flags)
> {
> if (bo->tiling_mode != I915_TILING_NONE && !(flags & MAP_RAW))
> return brw_bo_map_gtt(brw, bo, flags);
> - else if (can_map_cpu(bo, flags))
> - return brw_bo_map_cpu(brw, bo, flags);
> +
> + void *map;
> +
> + if (can_map_cpu(bo, flags))
> + map = brw_bo_map_cpu(brw, bo, flags);
> else
> - return brw_bo_map_gtt(brw, bo, flags);
> + map = brw_bo_map_wc(brw, bo, flags);
> +
> + /* Allow the attempt to fail by falling back to the GTT where necessary.
> + *
> + * Not every buffer can be mmaped directly using the CPU (or WC), for
> + * example buffers that wrap stolen memory or are imported from other
> + * devices. For those, we have little choice but to use a GTT mmapping.
> + * However, if we use a slow GTT mmapping for reads where we expected fast
> + * access, that order of magnitude difference in throughput will be
> clearly
> + * expressed by angry users.
> + */
> + if (!map) {
One more issue, we should not supply a GTT fallback for MAP_RAW (at
least not without removing the fence detiling), so this should be
if (!map && !(flags & MAP_RAW)) {
-Chris
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