[Mesa-dev] [PATCH V2] i965 : Optimize atom state flag checks

[Ian Romanick]

On 07/20/2017 04:35 AM, aravindan.muthukumar at intel.com wrote:
> From: Aravindan Muthukumar <aravindan.muthukumar at intel.com>
> 
> This patch improves CPI Rate(Cycles per Instruction)
> and branch mispredict for i965. The function check_state()
> was showing CPI retired rate.
> 
> Performance stats with android:
> CPI retired lowered by 28% (lower is better)
> Branch missprediction lowered by 13% (lower is better)
> 3DMark improved by 2%
> 
> The dissassembly doesn't show difference, although above
> results were observed with patch.
> 
> Signed-off-by: Aravindan Muthukumar <aravindan.muthukumar at intel.com>
> Signedd-off-by: Yogesh Marathe <yogesh.marathe at intel.com>

  Signed-off-by

> Tested-by: Asish <asish at intel.com>
> ---
> 
> Changes since V1:
> - Removed memset() change
> - Changed commit message as per review comments

This information should be in the main part of the commit message.

> 
>  src/mesa/drivers/dri/i965/brw_defines.h      |  4 ++++
>  src/mesa/drivers/dri/i965/brw_state_upload.c | 12 ++++++++----
>  2 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_defines.h b/src/mesa/drivers/dri/i965/brw_defines.h
> index 2a8dbf8..8c9a510 100644
> --- a/src/mesa/drivers/dri/i965/brw_defines.h
> +++ b/src/mesa/drivers/dri/i965/brw_defines.h
> @@ -1687,3 +1687,7 @@ enum brw_pixel_shader_coverage_mask_mode {
>  # define CSDBG2_CONSTANT_BUFFER_ADDRESS_OFFSET_DISABLE (1 << 4)
>  
>  #endif
> +
> +/* Checking the state of mesa and brw before emitting atoms */
> +#define CHECK_BRW_STATE(a,b) ((a.mesa & b.mesa) | (a.brw & b.brw))
> +
> diff --git a/src/mesa/drivers/dri/i965/brw_state_upload.c b/src/mesa/drivers/dri/i965/brw_state_upload.c
> index acaa97e..1c8b969 100644
> --- a/src/mesa/drivers/dri/i965/brw_state_upload.c
> +++ b/src/mesa/drivers/dri/i965/brw_state_upload.c
> @@ -443,10 +443,8 @@ check_and_emit_atom(struct brw_context *brw,
>                      struct brw_state_flags *state,
>                      const struct brw_tracked_state *atom)
>  {
> -   if (check_state(state, &atom->dirty)) {
>        atom->emit(brw);
>        merge_ctx_state(brw, state);
> -   }
>  }
>  
>  static inline void
> @@ -541,7 +539,10 @@ brw_upload_pipeline_state(struct brw_context *brw,
>  	 const struct brw_tracked_state *atom = &atoms[i];
>  	 struct brw_state_flags generated;
>  
> -         check_and_emit_atom(brw, &state, atom);
> +         /* Checking the state and emitting atoms */
> +         if (CHECK_BRW_STATE(state, atom->dirty)) {
> +            check_and_emit_atom(brw, &state, atom);
> +         }
>  
>  	 accumulate_state(&examined, &atom->dirty);
>  
> @@ -558,7 +559,10 @@ brw_upload_pipeline_state(struct brw_context *brw,
>        for (i = 0; i < num_atoms; i++) {
>  	 const struct brw_tracked_state *atom = &atoms[i];
>  
> -         check_and_emit_atom(brw, &state, atom);
> +         /* Checking the state and emitting atoms */
> +         if (CHECK_BRW_STATE(state, atom->dirty)) {
> +            check_and_emit_atom(brw, &state, atom);
> +         }
>        }
>     }
>  
>