[ovs-dev] [dpdk-latest PATCH] netdev-dpdk: add custom vhost statistics to count IRQs

[Eelco Chaudron]

When the dpdk vhost library executes an eventfd_write() call,
i.e. waking up the guest, a new callback will be called.

This patch adds the callback to count the number of
interrupts sent to the VM to track the number of times
interrupts where generated.

This might be of interest to find out system-calls were
called in the DPDK fast path.

The custom statistics can be seen with the following command:

  ovs-ofctl -O OpenFlow14 dump-ports <bridge> {<port>}

Signed-off-by: Eelco Chaudron <echaudro at redhat.com>
---
 lib/netdev-dpdk.c |   27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
index ba92e89..7ebbcdc 100644
--- a/lib/netdev-dpdk.c
+++ b/lib/netdev-dpdk.c
@@ -165,6 +165,8 @@ static int new_device(int vid);
 static void destroy_device(int vid);
 static int vring_state_changed(int vid, uint16_t queue_id, int enable);
 static void destroy_connection(int vid);
+static void vhost_guest_notified(int vid);
+
 static const struct vhost_device_ops virtio_net_device_ops =
 {
     .new_device =  new_device,
@@ -173,6 +175,7 @@ static const struct vhost_device_ops virtio_net_device_ops =
     .features_changed = NULL,
     .new_connection = NULL,
     .destroy_connection = destroy_connection,
+    .guest_notified = vhost_guest_notified,
 };
 
 enum { DPDK_RING_SIZE = 256 };
@@ -416,6 +419,8 @@ struct netdev_dpdk {
         struct netdev_stats stats;
         /* Custom stat for retries when unable to transmit. */
         uint64_t tx_retries;
+        /* Custom stat counting number of times a vhost remote was woken up */
+        uint64_t vhost_irqs;
         /* Protects stats */
         rte_spinlock_t stats_lock;
         /* 4 pad bytes here. */
@@ -2826,7 +2831,8 @@ netdev_dpdk_vhost_get_custom_stats(const struct netdev *netdev,
     int i;
 
 #define VHOST_CSTATS \
-    VHOST_CSTAT(tx_retries)
+    VHOST_CSTAT(tx_retries) \
+    VHOST_CSTAT(vhost_irqs)
 
 #define VHOST_CSTAT(NAME) + 1
     custom_stats->size = VHOST_CSTATS;
@@ -3746,6 +3752,25 @@ destroy_connection(int vid)
     }
 }
 
+static
+void vhost_guest_notified(int vid)
+{
+    struct netdev_dpdk *dev;
+
+    ovs_mutex_lock(&dpdk_mutex);
+    LIST_FOR_EACH (dev, list_node, &dpdk_list) {
+        if (netdev_dpdk_get_vid(dev) == vid) {
+            ovs_mutex_lock(&dev->mutex);
+            rte_spinlock_lock(&dev->stats_lock);
+            dev->vhost_irqs++;
+            rte_spinlock_unlock(&dev->stats_lock);
+            ovs_mutex_unlock(&dev->mutex);
+            break;
+        }
+    }
+    ovs_mutex_unlock(&dpdk_mutex);
+}
+
 /*
  * Retrieve the DPDK virtio device ID (vid) associated with a vhostuser
  * or vhostuserclient netdev.