> -----Original Message-----
> From: Eelco Chaudron <echau...@redhat.com>
> Sent: Wednesday, May 17, 2023 5:09 PM
> To: maxime.coque...@redhat.com; Xia, Chenbo <chenbo....@intel.com>;
> david.march...@redhat.com
> Cc: dev@dpdk.org
> Subject: [PATCH v3 2/4] vhost: make the guest_notifications statistic
> counter atomic
>
> Making the guest_notifications statistic counter atomic, allows
> it to be safely incremented while holding the read access_lock.
>
> Signed-off-by: Eelco Chaudron <echau...@redhat.com>
> ---
> lib/vhost/vhost.c | 8 ++++++++
> lib/vhost/vhost.h | 9 ++++++---
> 2 files changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
> index 74bdbfd810..8ff6434c93 100644
> --- a/lib/vhost/vhost.c
> +++ b/lib/vhost/vhost.c
> @@ -2086,6 +2086,10 @@ rte_vhost_vring_stats_get(int vid, uint16_t
> queue_id,
>
> rte_rwlock_write_lock(&vq->access_lock);
> for (i = 0; i < VHOST_NB_VQ_STATS; i++) {
> + /*
> + * No need to the read atomic counters as such, due to the
> + * above write access_lock preventing them to be updated.
> + */
> stats[i].value =
> *(uint64_t *)(((char *)vq) +
> vhost_vq_stat_strings[i].offset);
> stats[i].id = i;
> @@ -2112,6 +2116,10 @@ int rte_vhost_vring_stats_reset(int vid, uint16_t
> queue_id)
> vq = dev->virtqueue[queue_id];
>
> rte_rwlock_write_lock(&vq->access_lock);
> + /*
> + * No need to the reset atomic counters as such, due to the
> + * above write access_lock preventing them to be updated.
> + */
> memset(&vq->stats, 0, sizeof(vq->stats));
> rte_rwlock_write_unlock(&vq->access_lock);
>
> diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
> index 5c939ef06f..37609c7c8d 100644
> --- a/lib/vhost/vhost.h
> +++ b/lib/vhost/vhost.h
> @@ -135,11 +135,12 @@ struct virtqueue_stats {
> uint64_t broadcast;
> /* Size bins in array as RFC 2819, undersized [0], 64 [1], etc */
> uint64_t size_bins[8];
> - uint64_t guest_notifications;
> uint64_t iotlb_hits;
> uint64_t iotlb_misses;
> uint64_t inflight_submitted;
> uint64_t inflight_completed;
> + /* Counters below are atomic, and should be incremented as such. */
> + uint64_t guest_notifications;
> };
>
> /**
> @@ -907,7 +908,8 @@ vhost_vring_call_split(struct virtio_net *dev, struct
> vhost_virtqueue *vq)
> unlikely(!signalled_used_valid)) {
> eventfd_write(vq->callfd, (eventfd_t) 1);
> if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
> - vq->stats.guest_notifications++;
> +
> __atomic_fetch_add(&vq->stats.guest_notifications,
> + 1, __ATOMIC_RELAXED);
> if (dev->notify_ops->guest_notified)
> dev->notify_ops->guest_notified(dev->vid);
> }
> @@ -917,7 +919,8 @@ vhost_vring_call_split(struct virtio_net *dev, struct
> vhost_virtqueue *vq)
> && (vq->callfd >= 0)) {
> eventfd_write(vq->callfd, (eventfd_t)1);
> if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
> - vq->stats.guest_notifications++;
> +
> __atomic_fetch_add(&vq->stats.guest_notifications,
> + 1, __ATOMIC_RELAXED);
> if (dev->notify_ops->guest_notified)
> dev->notify_ops->guest_notified(dev->vid);
> }
Reviewed-by: Chenbo Xia <chenbo....@intel.com>
