[PATCH 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.coque...@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 470dadbba6..371c3e3858 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 db9985c9b9..b056c83d8f 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -2975,6 +2975,7 @@ 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;
@@ -3103,8 +3104,10 @@ 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];
@@ -3481,8 +3484,10 @@ 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]);
@@ -3729,8 +3734,10 @@ 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;
@@ -4019,8 +4026,10 @@ 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