[Mesa-dev] [PATCH 13/42] radeonsi: use a bitmask for tracking dirty atoms

[Grazvydas Ignotas]

On Sun, Aug 30, 2015 at 10:11 PM, Marek Olšák <maraeo at gmail.com> wrote:
...
> diff --git a/src/gallium/drivers/radeonsi/si_state_draw.c b/src/gallium/drivers/radeonsi/si_state_draw.c
> index 2ff58d1..81575b5 100644
> --- a/src/gallium/drivers/radeonsi/si_state_draw.c
> +++ b/src/gallium/drivers/radeonsi/si_state_draw.c
> @@ -729,7 +729,7 @@ void si_draw_vbo(struct pipe_context *ctx, const struct pipe_draw_info *info)
>  {
>         struct si_context *sctx = (struct si_context *)ctx;
>         struct pipe_index_buffer ib = {};
> -       unsigned i;
> +       unsigned mask;
>
>         if (!info->count && !info->indirect &&
>             (info->indexed || !info->count_from_stream_output))
> @@ -821,12 +821,13 @@ void si_draw_vbo(struct pipe_context *ctx, const struct pipe_draw_info *info)
>         si_need_cs_space(sctx, 0, TRUE);
>
>         /* Emit states. */
> -       for (i = 0; i < SI_NUM_ATOMS; i++) {
> -               if (sctx->atoms.array[i]->dirty) {
> -                       sctx->atoms.array[i]->emit(&sctx->b, sctx->atoms.array[i]);
> -                       sctx->atoms.array[i]->dirty = false;
> -               }
> +       mask = sctx->dirty_atoms;
> +       while (mask) {
> +               struct r600_atom *atom = sctx->atoms.array[u_bit_scan(&mask)];
> +
> +               atom->emit(&sctx->b, atom);
>         }
> +       sctx->dirty_atoms = 0;

It looks like sctx->atoms.array[i]->dirty is never cleared? Maybe we
should get rid of it then?

I wonder if multiple threads can end up touching the atoms? If so, we
might need to use atomic bit set/clear (__sync_or_and_fetch(), etc)
and something to read+clear sctx->dirty_atoms atomically above (xchg
instruction, not sure which helper in mesa could be used for this).

Gražvydas