radv: implement a fast prefetch path for the vertex stage

This allows to start draws as soon as possible.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>

diff --git a/src/amd/vulkan/radv_cmd_buffer.c b/src/amd/vulkan/radv_cmd_buffer.c
index 58d960e..526b618 100644 (file)
--- 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
@@ -3070,7 +3079,7 @@ 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
@@ -3079,8 +3088,11 @@ 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))
@@ -3088,6 +3100,14 @@ 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);