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vdpa/mlx5: fix polling threads scheduling

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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 <matan@nvidia.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Xueming Li <xuemingl@nvidia.com>
This commit is contained in:
Matan Azrad 2021-02-08 09:28:01 +00:00 committed by Thomas Monjalon
parent 894028ace2
commit b7fa0bf4d5
1 changed files with 16 additions and 0 deletions
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16
drivers/vdpa/mlx5/mlx5_vdpa_event.c
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@ -232,6 +232,9 @@ mlx5_vdpa_timer_sleep(struct mlx5_vdpa_priv *priv, uint32_t max)
}
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 @@ mlx5_vdpa_cqe_event_setup(struct mlx5_vdpa_priv *priv)
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 @@ mlx5_vdpa_cqe_event_setup(struct mlx5_vdpa_priv *priv)
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) {