[Mesa-dev] [PATCH v2 5/8] i965 gen6: Allocate URB space for GS

Eric Anholt eric at anholt.net
Wed Dec 7 13:22:54 PST 2011

On Wed,  7 Dec 2011 11:09:13 -0800, Paul Berry <stereotype441 at gmail.com> wrote:
> When the GS is not in use, the entire URB space is available for the
> VS.  When the GS is in use, we split the URB space 50/50.
> The 50/50 split is probably not optimal--we'll probably want tune this
> for performance in a future patch.  For example, in most situations,
> it's probably worth allocating more than 50% of the space to the VS,
> since VS space is used for vertex caching.  But for now this is good
> enough.

>     assert(brw->urb.nr_vs_entries >= 24);

Looks like we'll still be OK in the worst case here: 32KB URB / 2 / (24
entries/URB) / (16 bytes/attribute) = 42 attributes/entry, which is more
than we expose even with rounding of entry size and the things in the
VUE that aren't attributes.

Reviewed-by: Eric Anholt <eric at anholt.net>
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