On 2/8/21 10:28 AM, Matan Azrad wrote:
> When the event mode is with 0 fixed delay, the polling-thread will never
> give-up CPU.
>
> So, when multi-polling-threads are active, the context-switch between
> them will be managed by the system which may affect latency according to
> the time-out decided by the system.
>
> In order to fix multi-devices polling thread scheduling, this patch
> forces rescheduling for each CQ poll iteration.
>
> Move the polling thread to SCHED_RR mode with maximum priority to
> complete the fairness.
>
> Fixes: 6956a48cabbb ("vdpa/mlx5: set polling mode default delay to zero")
>
> Signed-off-by: Matan Azrad <ma...@nvidia.com>
> ---
> drivers/vdpa/mlx5/mlx5_vdpa_event.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/drivers/vdpa/mlx5/mlx5_vdpa_event.c
> b/drivers/vdpa/mlx5/mlx5_vdpa_event.c
> index 0f635ff..86adc86 100644
> --- a/drivers/vdpa/mlx5/mlx5_vdpa_event.c
> +++ b/drivers/vdpa/mlx5/mlx5_vdpa_event.c
> @@ -232,6 +232,9 @@
> }
> if (priv->timer_delay_us)
> usleep(priv->timer_delay_us);
> + else
> + /* Give-up CPU to improve polling threads scheduling. */
> + pthread_yield();
> }
>
> static void *
> @@ -500,6 +503,9 @@
> rte_cpuset_t cpuset;
> pthread_attr_t attr;
> char name[16];
> + const struct sched_param sp = {
> + .sched_priority = sched_get_priority_max(SCHED_RR),
> + };
>
> if (!priv->eventc)
> /* All virtqs are in poll mode. */
> @@ -520,6 +526,16 @@
> DRV_LOG(ERR, "Failed to set thread affinity.");
> return -1;
> }
> + ret = pthread_attr_setschedpolicy(&attr, SCHED_RR);
> + if (ret) {
> + DRV_LOG(ERR, "Failed to set thread sched policy = RR.");
> + return -1;
> + }
> + ret = pthread_attr_setschedparam(&attr, &sp);
> + if (ret) {
> + DRV_LOG(ERR, "Failed to set thread priority.");
> + return -1;
> + }
> ret = pthread_create(&priv->timer_tid, &attr,
> mlx5_vdpa_poll_handle, (void *)priv);
> if (ret) {
>
Reviewed-by: Maxime Coquelin <maxime.coque...@redhat.com>
