[Mesa-dev] [PATCH 03/11] radeonsi: decrease the number of compiler threads to num CPUs - 1

[Grazvydas Ignotas]

With the "core wars" starting (16core/32thread "consumer" CPUs
announced), maybe it's time to add an upper limit? Waking up a core
from low power state has it's latency, it's sometimes faster to just
do several jobs on an active core than to wake another one (which will
also cause more lock contention, the core will just see the job was
already taken by someone else and go back to sleep).

Gražvydas

On Thu, Jun 1, 2017 at 9:18 PM, Marek Olšák <maraeo at gmail.com> wrote:
> From: Marek Olšák <marek.olsak at amd.com>
>
> Reserve one core for other things (like draw calls).
> ---
>  src/gallium/drivers/radeonsi/si_pipe.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/src/gallium/drivers/radeonsi/si_pipe.c b/src/gallium/drivers/radeonsi/si_pipe.c
> index de4e5da..4704304 100644
> --- a/src/gallium/drivers/radeonsi/si_pipe.c
> +++ b/src/gallium/drivers/radeonsi/si_pipe.c
> @@ -874,22 +874,25 @@ struct pipe_screen *radeonsi_screen_create(struct radeon_winsys *ws)
>
>         si_init_screen_state_functions(sscreen);
>
>         if (!r600_common_screen_init(&sscreen->b, ws) ||
>             !si_init_gs_info(sscreen) ||
>             !si_init_shader_cache(sscreen)) {
>                 FREE(sscreen);
>                 return NULL;
>         }
>
> -       /* Only enable as many threads as we have target machines and CPUs. */
> +       /* Only enable as many threads as we have target machines, but at most
> +        * the number of CPUs - 1 if there is more than one.
> +        */
>         num_cpus = sysconf(_SC_NPROCESSORS_ONLN);
> +       num_cpus = MAX2(1, num_cpus - 1);
>         num_compiler_threads = MIN2(num_cpus, ARRAY_SIZE(sscreen->tm));
>
>         if (!util_queue_init(&sscreen->shader_compiler_queue, "si_shader",
>                              32, num_compiler_threads)) {
>                 si_destroy_shader_cache(sscreen);
>                 FREE(sscreen);
>                 return NULL;
>         }
>
>         si_handle_env_var_force_family(sscreen);
> --
> 2.7.4
>
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