[Mesa-dev] [v2 4/9] i965: Estimate batch space per shader stage

[Jason Ekstrand]

On Tue, Jan 31, 2017 at 8:15 AM, Topi Pohjolainen <
topi.pohjolainen at gmail.com> wrote:

> Current estimate doesn't consider space needed for surface states
> and it only calculates for one shader stage. Each stage can have
> its own sampler and surface state configuration.
>
> While this is only matter of runtime dynamics we don't seem to hit
> it currently. However, this becomes visible with blorp tex uploads
> (HSW with piglit test max-samplers). One runs out of space while
> batch wrapping isn't allowed.
>
> v2: Rebase on top of current upstream
>
> Signed-off-by: Topi Pohjolainen <topi.pohjolainen at intel.com>
> CC: Kenneth Graunke <kenneth at whitecape.org>
> CC: Jason Ekstrand <jason at jlekstrand.net>
> ---
>  src/mesa/drivers/dri/i965/brw_draw.c | 49 ++++++++++++++++++++++++++++++
> +++---
>  1 file changed, 46 insertions(+), 3 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_draw.c
> b/src/mesa/drivers/dri/i965/brw_draw.c
> index 0db7311..83a9f33 100644
> --- a/src/mesa/drivers/dri/i965/brw_draw.c
> +++ b/src/mesa/drivers/dri/i965/brw_draw.c
> @@ -395,6 +395,51 @@ brw_postdraw_set_buffers_need_resolve(struct
> brw_context *brw)
>     }
>  }
>
> +static unsigned
> +brw_get_num_active_samplers(const struct gl_context *ctx,
> +                            const struct gl_program *prog)
> +{
> +   const unsigned last = util_last_bit(prog->SamplersUsed);
> +   unsigned count = 0;
> +
> +   for (unsigned s = 0; s < last; s++) {
> +      if (prog->SamplersUsed & (1 << s)) {
> +         const unsigned unit = prog->SamplerUnits[s];
> +         if (ctx->Texture.Unit[unit]._Current)
> +            ++count;
> +      }
> +   }
> +
> +   return count;
> +}
> +
> +static unsigned
> +brw_estimate_batch_space_for_textures(const struct brw_context *brw)
> +{
> +   const struct gl_context *ctx = &brw->ctx;
> +   unsigned total = 0;
> +
> +   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
> +      const struct gl_program *prog = ctx->_Shader->CurrentProgram[i];
> +
> +      if (prog == NULL)
> +         continue;
> +
> +      const unsigned num_samplers = brw_get_num_active_samplers(ctx,
> prog);
> +      const unsigned sampler_needs_per_tex_unit =
> +         16 /* sampler_state_size */ +
> +         sizeof(struct gen5_sampler_default_color);
> +      const unsigned surface_state_needs_per_tex_unit =
> +         ALIGN(brw->isl_dev.ss.size, brw->isl_dev.ss.align) +
> +         4 /* binding table pointer */;
> +      const unsigned total_per_tex_unit = sampler_needs_per_tex_unit +
> +                                          surface_state_needs_per_tex_
> unit;
> +      total += (num_samplers * total_per_tex_unit);
>

This isn't exactly correct.  While it's true that a binding table entry
only consumes 4 bytes, binding table sizes have to be rounded up to 64B so,
if you have a number of samplers that is not a multiple of 16, this will
underestimate.


> +   }
> +
> +   return total;
> +}
> +
>  /* May fail if out of video memory for texture or vbo upload, or on
>   * fallback conditions.
>   */
> @@ -477,11 +522,9 @@ brw_try_draw_prims(struct gl_context *ctx,
>
>     for (i = 0; i < nr_prims; i++) {
>        int estimated_max_prim_size;
> -      const int sampler_state_size = 16;
>
>        estimated_max_prim_size = 512; /* batchbuffer commands */
> -      estimated_max_prim_size += BRW_MAX_TEX_UNIT *
> -         (sampler_state_size + sizeof(struct gen5_sampler_default_color));
> +      estimated_max_prim_size += brw_estimate_batch_space_for_
> textures(brw);
>        estimated_max_prim_size += 1024; /* gen6 VS push constants */
>        estimated_max_prim_size += 1024; /* gen6 WM push constants */
>        estimated_max_prim_size += 512; /* misc. pad */
> --
> 2.5.5
>
>
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