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) {
--
1.8.3.1
