[v2,2/3] vhost: make the guest_notifications statistic counter atomic.
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Commit Message
Making the guest_notifications statistic counter atomic, allows
it to be safely incremented while holding the read access_lock.
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
---
lib/vhost/vhost.c | 8 ++++++++
lib/vhost/vhost.h | 9 ++++++---
2 files changed, 14 insertions(+), 3 deletions(-)
@@ -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);
@@ -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);
}