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

[Jason Ekstrand]

On Tue, Jan 31, 2017 at 10:38 AM, Jason Ekstrand <jason at jlekstrand.net>
wrote:

>
> 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.
>>
>
Also, what happens when this case is triggered?  Do we assert fail?  GPU
Hang?  Just nicely handle it by flushing the batch?

--Jason


> 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_un
>> it;
>> +      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_t
>> extures(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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