[Mesa-dev] [PATCH 3/3] radv: implement a fast prefetch path for the vertex stage

[Dieter Nützel]

For the series:

Tested-by: Dieter Nützel <Dieter at nuetzel-hh.de>

on Polaris 20 / RX580
with F1 2017, smoketest

Dieter

Am 04.04.2018 12:12, schrieb Samuel Pitoiset:
> This allows to start draws as soon as possible.
> 
> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
> ---
>  src/amd/vulkan/radv_cmd_buffer.c | 40 
> ++++++++++++++++++++++++++++++----------
>  1 file changed, 30 insertions(+), 10 deletions(-)
> 
> diff --git a/src/amd/vulkan/radv_cmd_buffer.c 
> b/src/amd/vulkan/radv_cmd_buffer.c
> index 393d9ba4f4..0e59f99799 100644
> --- a/src/amd/vulkan/radv_cmd_buffer.c
> +++ b/src/amd/vulkan/radv_cmd_buffer.c
> @@ -640,39 +640,48 @@ radv_emit_shader_prefetch(struct radv_cmd_buffer
> *cmd_buffer,
> 
>  static void
>  radv_emit_prefetch_L2(struct radv_cmd_buffer *cmd_buffer,
> -		      struct radv_pipeline *pipeline)
> +		      struct radv_pipeline *pipeline,
> +		      bool vertex_stage_only)
>  {
>  	struct radv_cmd_state *state = &cmd_buffer->state;
> +	uint32_t mask = state->prefetch_L2_mask;
> 
>  	if (cmd_buffer->device->physical_device->rad_info.chip_class < CIK)
>  		return;
> 
> -	if (state->prefetch_L2_mask & RADV_PREFETCH_VS)
> +	if (vertex_stage_only) {
> +		/* Fast prefetch path for starting draws as soon as possible.
> +		 */
> +		mask = state->prefetch_L2_mask & (RADV_PREFETCH_VS |
> +						  RADV_PREFETCH_VBO_DESCRIPTORS);
> +	}
> +
> +	if (mask & RADV_PREFETCH_VS)
>  		radv_emit_shader_prefetch(cmd_buffer,
>  					  pipeline->shaders[MESA_SHADER_VERTEX]);
> 
> -	if (state->prefetch_L2_mask & RADV_PREFETCH_VBO_DESCRIPTORS)
> +	if (mask & RADV_PREFETCH_VBO_DESCRIPTORS)
>  		si_cp_dma_prefetch(cmd_buffer, state->vb_va, state->vb_size);
> 
> -	if (state->prefetch_L2_mask & RADV_PREFETCH_TCS)
> +	if (mask & RADV_PREFETCH_TCS)
>  		radv_emit_shader_prefetch(cmd_buffer,
>  					  pipeline->shaders[MESA_SHADER_TESS_CTRL]);
> 
> -	if (state->prefetch_L2_mask & RADV_PREFETCH_TES)
> +	if (mask & RADV_PREFETCH_TES)
>  		radv_emit_shader_prefetch(cmd_buffer,
>  					  pipeline->shaders[MESA_SHADER_TESS_EVAL]);
> 
> -	if (state->prefetch_L2_mask & RADV_PREFETCH_GS) {
> +	if (mask & RADV_PREFETCH_GS) {
>  		radv_emit_shader_prefetch(cmd_buffer,
>  					  pipeline->shaders[MESA_SHADER_GEOMETRY]);
>  		radv_emit_shader_prefetch(cmd_buffer, pipeline->gs_copy_shader);
>  	}
> 
> -	if (state->prefetch_L2_mask & RADV_PREFETCH_PS)
> +	if (mask & RADV_PREFETCH_PS)
>  		radv_emit_shader_prefetch(cmd_buffer,
>  					  pipeline->shaders[MESA_SHADER_FRAGMENT]);
> 
> -	state->prefetch_L2_mask = 0;
> +	state->prefetch_L2_mask &= ~mask;
>  }
> 
>  static void
> @@ -3042,7 +3051,7 @@ radv_draw(struct radv_cmd_buffer *cmd_buffer,
>  		 */
>  		if (cmd_buffer->state.prefetch_L2_mask) {
>  			radv_emit_prefetch_L2(cmd_buffer,
> -					      cmd_buffer->state.pipeline);
> +					      cmd_buffer->state.pipeline, false);
>  		}
>  	} else {
>  		/* If we don't wait for idle, start prefetches first, then set
> @@ -3051,8 +3060,11 @@ radv_draw(struct radv_cmd_buffer *cmd_buffer,
>  		si_emit_cache_flush(cmd_buffer);
> 
>  		if (cmd_buffer->state.prefetch_L2_mask) {
> +			/* Only prefetch the vertex shader and VBO descriptors
> +			 * in order to start the draw as soon as possible.
> +			 */
>  			radv_emit_prefetch_L2(cmd_buffer,
> -					      cmd_buffer->state.pipeline);
> +					      cmd_buffer->state.pipeline, true);
>  		}
> 
>  		if (!radv_upload_graphics_shader_descriptors(cmd_buffer, 
> pipeline_is_dirty))
> @@ -3060,6 +3072,14 @@ radv_draw(struct radv_cmd_buffer *cmd_buffer,
> 
>  		radv_emit_all_graphics_states(cmd_buffer, info);
>  		radv_emit_draw_packets(cmd_buffer, info);
> +
> +		/* Prefetch the remaining shaders after the draw has been
> +		 * started.
> +		 */
> +		if (cmd_buffer->state.prefetch_L2_mask) {
> +			radv_emit_prefetch_L2(cmd_buffer,
> +					      cmd_buffer->state.pipeline, false);
> +		}
>  	}
> 
>  	assert(cmd_buffer->cs->cdw <= cdw_max);