[Mesa-dev] [PATCH] i965/bxt: Fix conservative wm thread counts.

[Kenneth Graunke]

On Monday, January 25, 2016 12:34:15 PM PST Ben Widawsky wrote:
> When setting the conservative thread counts, I halved everything. That isn't
> correct for the wm, which has nothing to do with actual thread counts. I 
suck.
> 
> BXT only has 1 slice, and there is some ambiguity about subslices, so just
> reserve the max possible for now. It looks like this might fix:
> piglit.spec.glsl-1_50.execution.variable-indexing.gs-output-array-vec4-
index-wr.bxtm64.
> I kind of question why that is, but it is what Jenkins says.
> 
> Mark is current running some of the other blacklisted tests on this patch. 
(it
> effects anything requiring scratch space).
> 
> Cc: mesa-stable <mesa-stable at lists.freedesktop.org>
> Cc: Kenneth Graunke <kenneth at whitecape.org>
> Cc: Neil Roberts <neil at linux.intel.com>
> Cc: Mark Janes <mark.a.janes at intel.com>
> Signed-off-by: Ben Widawsky <benjamin.widawsky at intel.com>
> ---
>  src/mesa/drivers/dri/i965/brw_device_info.c | 2 +-
>  1 file changed, 1 insertion(+), 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 b8148bf..7ab70fe 100644
> --- a/src/mesa/drivers/dri/i965/brw_device_info.c
> +++ b/src/mesa/drivers/dri/i965/brw_device_info.c
> @@ -390,7 +390,7 @@ static const struct brw_device_info brw_device_info_bxt 
= {
>     .max_hs_threads = 56,
>     .max_ds_threads = 56,
>     .max_gs_threads = 56,
> -   .max_wm_threads = 32,
> +   .max_wm_threads = 64 * 3,
>     .max_cs_threads = 28,
>     .urb = {
>        .size = 64,
> 

I haven't verified the values, but 32 is clearly too small.
From memory, I suspect that test uses spilling, and you won't
allocate enough scratch space if max_wm_threads is set too low.

Acked-by: Kenneth Graunke <kenneth at whitecape.org>

Now that we have the number of slices/subslices/whatever for compute
shaders, it might make sense to use that info to compute scratch space
requirements in the future.  *shrug*
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