[Mesa-dev] [PATCH] i965/skl: Use larger URB size where available.

[Jordan Justen]

On 2015-09-10 16:59:12, Ben Widawsky wrote:
> All SKL SKUs except the lowest one which has half the L3 size actually have 384K

These commit message lines seem to wrap a bit long. This first line is
80 characters.

> of URB per slice.
> 
> For once, I can explain how this mistake was made and how it was missed in
> review...  Historically when we enable a platform and put the production sizes,
> you can simply look at the "smallest" SKU and see what its URB size is (and we
> assumed it was the 1 slice variant). Since on newer platforms the URB sizes are
> scaled automatically by HW, this was sufficient. On SKL, this is a bit different
> as the lowest SKU actually has half of the L3 fused off. GT2 is the 1 slice (not
> GT1) variant and it has 384K.
> 
> There are no Jenkins tests fixed (or regressions) and we don't expect any fixes
> here because you can always run with less URB size - this potentially improves
> performance.

It would be nice if we were able to find a benchmark that improves
from this change. If we can't then maybe we should just remove this
paragraph. It seems like the right change regardless.

Reviewed-by: Jordan Justen <jordan.l.justen at intel.com>

> Thanks to Sarah for bringing this to my attention.

Reported-by?

> Cc: "10.6 11.0" <mesa-stable at lists.freedesktop.org>
> Cc: Neil Roberts <neil at linux.intel.com>
> Cc: Sarah Sharp <sarah.a.sharp at intel.com>
> Cc: Jordan Justen <jordan.l.justen at intel.com>
> Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> ---
>  src/mesa/drivers/dri/i965/brw_device_info.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_device_info.c b/src/mesa/drivers/dri/i965/brw_device_info.c
> index 7ad3a2f..a6a3bb6 100644
> --- a/src/mesa/drivers/dri/i965/brw_device_info.c
> +++ b/src/mesa/drivers/dri/i965/brw_device_info.c
> @@ -314,7 +314,7 @@ static const struct brw_device_info brw_device_info_chv = {
>     .max_wm_threads = 64 * 6,                        \
>     .max_cs_threads = 56,                            \
>     .urb = {                                         \
> -      .size = 192,                                  \
> +      .size = 384,                                  \
>        .min_vs_entries = 64,                         \
>        .max_vs_entries = 1856,                       \
>        .max_hs_entries = 672,                        \
> @@ -324,6 +324,7 @@ static const struct brw_device_info brw_device_info_chv = {
>  
>  static const struct brw_device_info brw_device_info_skl_gt1 = {
>     GEN9_FEATURES, .gt = 1,
> +   .urb.size = 192,
>  };
>  
>  static const struct brw_device_info brw_device_info_skl_gt2 = {
> -- 
> 2.5.1
>