[Mesa-dev] [PATCH v3 18/18] anv/cmd_buffer: Avoid unnecessary transitions before fast clears

[Nanley Chery]

On Wed, Feb 14, 2018 at 12:16:33PM -0800, Jason Ekstrand wrote:
> Previously, we would always apply the layout transition at the beginning
> of the subpass and then do the clear whether fast or slow.  This meant
> that there were some cases, specifically when the initial layout is
> VK_IMAGE_LAYOUT_UNDEFINED, where we would end up doing a fast-clear or
> ambiguate followed immediately by a fast-clear.  This probably isn't
> terribly expensive, but it is a waste that we can avoid easily enough
> now that we're doing everything at the same time in begin_subpass.
> ---
>  src/intel/vulkan/genX_cmd_buffer.c | 62 +++++++++++++++++++++++---------------
>  1 file changed, 38 insertions(+), 24 deletions(-)
> 
> diff --git a/src/intel/vulkan/genX_cmd_buffer.c b/src/intel/vulkan/genX_cmd_buffer.c
> index 7f06441..453aea8 100644
> --- a/src/intel/vulkan/genX_cmd_buffer.c
> +++ b/src/intel/vulkan/genX_cmd_buffer.c
> @@ -3335,6 +3335,12 @@ cmd_buffer_begin_subpass(struct anv_cmd_buffer *cmd_buffer,
>           target_layout = subpass->attachments[i].layout;
>        }
>  
> +      /* Clears are based on the image view for 3D surfaces but transitions
> +       * are done on an entire miplevel at a time.
> +       */
> +      uint32_t base_clear_layer = iview->planes[0].isl.base_array_layer;
> +      uint32_t clear_layer_count = fb->layers;
> +
>        if (image->aspects & VK_IMAGE_ASPECT_ANY_COLOR_BIT_ANV) {
>           assert(image->aspects == VK_IMAGE_ASPECT_COLOR_BIT);
>  
> @@ -3348,30 +3354,8 @@ cmd_buffer_begin_subpass(struct anv_cmd_buffer *cmd_buffer,
>              layer_count = fb->layers;
>           }
>  
> -         transition_color_buffer(cmd_buffer, image, VK_IMAGE_ASPECT_COLOR_BIT,
> -                                 iview->planes[0].isl.base_level, 1,
> -                                 base_layer, layer_count,
> -                                 att_state->current_layout, target_layout);
> -      } else if (image->aspects & VK_IMAGE_ASPECT_DEPTH_BIT) {
> -         transition_depth_buffer(cmd_buffer, image,
> -                                 att_state->current_layout, target_layout);
> -         att_state->aux_usage =
> -            anv_layout_to_aux_usage(&cmd_buffer->device->info, image,
> -                                    VK_IMAGE_ASPECT_DEPTH_BIT, target_layout);
> -      }
> -      att_state->current_layout = target_layout;
> -
> -      if (att_state->pending_clear_aspects & VK_IMAGE_ASPECT_COLOR_BIT) {
> -         assert(att_state->pending_clear_aspects == VK_IMAGE_ASPECT_COLOR_BIT);
> -
> -         /* Multi-planar images are not supported as attachments */
> -         assert(image->aspects == VK_IMAGE_ASPECT_COLOR_BIT);
> -         assert(image->n_planes == 1);
> -
> -         uint32_t base_clear_layer = iview->planes[0].isl.base_array_layer;
> -         uint32_t clear_layer_count = fb->layers;
> -
> -         if (att_state->fast_clear) {
> +         if ((att_state->pending_clear_aspects & VK_IMAGE_ASPECT_COLOR_BIT) &&
> +             att_state->fast_clear) {
>              /* We only support fast-clears on the first layer */
>              assert(iview->planes[0].isl.base_level == 0);
>              assert(iview->planes[0].isl.base_array_layer == 0);
> @@ -3381,6 +3365,13 @@ cmd_buffer_begin_subpass(struct anv_cmd_buffer *cmd_buffer,
>              base_clear_layer++;
>              clear_layer_count--;
>  
> +            /* Performing a fast clear takes care of all our transition needs
> +             * for the first slice.  Increment the base layer and layer count
> +             * so that later transitions don't touch layer 0.
> +             */

Why not do the same optimization for depth?

-Nanley

> +            base_layer++;
> +            layer_count--;
> +
>              genX(copy_fast_clear_dwords)(cmd_buffer, att_state->color.state,
>                                           image, VK_IMAGE_ASPECT_COLOR_BIT,
>                                           true /* copy from ss */);
> @@ -3401,6 +3392,29 @@ cmd_buffer_begin_subpass(struct anv_cmd_buffer *cmd_buffer,
>              }
>           }
>  
> +         if (layer_count > 0) {
> +            transition_color_buffer(cmd_buffer, image,
> +                                    VK_IMAGE_ASPECT_COLOR_BIT,
> +                                    iview->planes[0].isl.base_level, 1,
> +                                    base_layer, layer_count,
> +                                    att_state->current_layout, target_layout);
> +         }
> +      } else if (image->aspects & VK_IMAGE_ASPECT_DEPTH_BIT) {
> +         transition_depth_buffer(cmd_buffer, image,
> +                                 att_state->current_layout, target_layout);
> +         att_state->aux_usage =
> +            anv_layout_to_aux_usage(&cmd_buffer->device->info, image,
> +                                    VK_IMAGE_ASPECT_DEPTH_BIT, target_layout);
> +      }
> +      att_state->current_layout = target_layout;
> +
> +      if (att_state->pending_clear_aspects & VK_IMAGE_ASPECT_COLOR_BIT) {
> +         assert(att_state->pending_clear_aspects == VK_IMAGE_ASPECT_COLOR_BIT);
> +
> +         /* Multi-planar images are not supported as attachments */
> +         assert(image->aspects == VK_IMAGE_ASPECT_COLOR_BIT);
> +         assert(image->n_planes == 1);
> +
>           if (clear_layer_count > 0) {
>              assert(image->n_planes == 1);
>              anv_image_clear_color(cmd_buffer, image, VK_IMAGE_ASPECT_COLOR_BIT,
> -- 
> 2.5.0.400.gff86faf
> 
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