[PATCH v2 2/2] vhost: add new mbuf allocation failure statistic

[Maxime Coquelin]

This patch introduces a new, per virtqueue, mbuf allocation
failure statistic. It can be useful to troubleshoot packets
drops due to insufficient mempool size or memory leaks.

Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
---
 lib/vhost/vhost.c      |  1 +
 lib/vhost/vhost.h      |  1 +
 lib/vhost/virtio_net.c | 17 +++++++++++++----
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
index 5912a42979..ac71d17784 100644
--- a/lib/vhost/vhost.c
+++ b/lib/vhost/vhost.c
@@ -55,6 +55,7 @@ static const struct vhost_vq_stats_name_off vhost_vq_stat_strings[] = {
 	{"iotlb_misses",           offsetof(struct vhost_virtqueue, stats.iotlb_misses)},
 	{"inflight_submitted",     offsetof(struct vhost_virtqueue, stats.inflight_submitted)},
 	{"inflight_completed",     offsetof(struct vhost_virtqueue, stats.inflight_completed)},
+	{"mbuf_alloc_failed",      offsetof(struct vhost_virtqueue, stats.mbuf_alloc_failed)},
 };
 
 #define VHOST_NB_VQ_STATS RTE_DIM(vhost_vq_stat_strings)
diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
index 16fe6d4ddb..82ea25b3e1 100644
--- a/lib/vhost/vhost.h
+++ b/lib/vhost/vhost.h
@@ -156,6 +156,7 @@ struct virtqueue_stats {
 	uint64_t iotlb_misses;
 	uint64_t inflight_submitted;
 	uint64_t inflight_completed;
+	uint64_t mbuf_alloc_failed;
 	uint64_t guest_notifications_suppressed;
 	/* Counters below are atomic, and should be incremented as such. */
 	RTE_ATOMIC(uint64_t) guest_notifications;
diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index 9951842b9f..1359c5fb1f 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -2996,6 +2996,7 @@ desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		if (mbuf_avail == 0) {
 			cur = rte_pktmbuf_alloc(mbuf_pool);
 			if (unlikely(cur == NULL)) {
+				vq->stats.mbuf_alloc_failed++;
 				VHOST_DATA_LOG(dev->ifname, ERR,
 					"failed to allocate memory for mbuf.");
 				goto error;
@@ -3123,8 +3124,10 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	count = RTE_MIN(count, avail_entries);
 	VHOST_DATA_LOG(dev->ifname, DEBUG, "about to dequeue %u buffers", count);
 
-	if (rte_pktmbuf_alloc_bulk(mbuf_pool, pkts, count))
+	if (rte_pktmbuf_alloc_bulk(mbuf_pool, pkts, count)) {
+		vq->stats.mbuf_alloc_failed += count;
 		return 0;
+	}
 
 	for (i = 0; i < count; i++) {
 		struct buf_vector buf_vec[BUF_VECTOR_MAX];
@@ -3494,8 +3497,10 @@ virtio_dev_tx_packed(struct virtio_net *dev,
 {
 	uint32_t pkt_idx = 0;
 
-	if (rte_pktmbuf_alloc_bulk(mbuf_pool, pkts, count))
+	if (rte_pktmbuf_alloc_bulk(mbuf_pool, pkts, count)) {
+		vq->stats.mbuf_alloc_failed += count;
 		return 0;
+	}
 
 	do {
 		rte_prefetch0(&vq->desc_packed[vq->last_avail_idx]);
@@ -3745,8 +3750,10 @@ virtio_dev_tx_async_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	count = RTE_MIN(count, avail_entries);
 	VHOST_DATA_LOG(dev->ifname, DEBUG, "about to dequeue %u buffers", count);
 
-	if (rte_pktmbuf_alloc_bulk(mbuf_pool, pkts_prealloc, count))
+	if (rte_pktmbuf_alloc_bulk(mbuf_pool, pkts_prealloc, count)) {
+		vq->stats.mbuf_alloc_failed += count;
 		goto out;
+	}
 
 	for (pkt_idx = 0; pkt_idx < count; pkt_idx++) {
 		uint16_t head_idx = 0;
@@ -4035,8 +4042,10 @@ virtio_dev_tx_async_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 
 	async_iter_reset(async);
 
-	if (rte_pktmbuf_alloc_bulk(mbuf_pool, pkts_prealloc, count))
+	if (rte_pktmbuf_alloc_bulk(mbuf_pool, pkts_prealloc, count)) {
+		vq->stats.mbuf_alloc_failed += count;
 		goto out;
+	}
 
 	do {
 		struct rte_mbuf *pkt = pkts_prealloc[pkt_idx];
-- 
2.43.0