[ovs-dev] [PATCH v9 2/2] netdev-dpdk:Detailed packet drop statistics

Sriram Vatala sriram.v at altencalsoftlabs.com
Sat Sep 21 02:40:08 UTC 2019


OVS may be unable to transmit packets for multiple reasons and
today there is a single counter to track packets dropped due to
any of those reasons. The most common reason is that a VM is
unable to read packets fast enough causing the vhostuser port
transmit queue on the OVS side to become full. This manifests
as a problem with VNFs not receiving all packets. Having a
separate drop counter to track packets dropped because the
transmit queue is full will clearly indicate that the problem
is on the VM side and not in OVS. Similarly maintaining separate
counters for all possible drops helps in indicating sensible
cause for packet drops.

This patch adds custom software stats counters to track packets
dropped at port level and these counters are displayed along with
other stats in "ovs-vsctl get interface <iface> statistics"
command. The detailed stats will be available for both dpdk and
vhostuser ports.

--
Changes since v8:
Addressed comments given by Ilya.

Signed-off-by: Sriram Vatala <sriram.v at altencalsoftlabs.com>
---
 Documentation/topics/dpdk/vhost-user.rst      | 13 ++-
 lib/netdev-dpdk.c                             | 81 +++++++++++++++----
 utilities/bugtool/automake.mk                 |  3 +-
 utilities/bugtool/ovs-bugtool-get-port-stats  | 25 ++++++
 .../plugins/network-status/openvswitch.xml    |  1 +
 5 files changed, 105 insertions(+), 18 deletions(-)
 create mode 100755 utilities/bugtool/ovs-bugtool-get-port-stats

diff --git a/Documentation/topics/dpdk/vhost-user.rst b/Documentation/topics/dpdk/vhost-user.rst
index 724aa62f6..89388a2bf 100644
--- a/Documentation/topics/dpdk/vhost-user.rst
+++ b/Documentation/topics/dpdk/vhost-user.rst
@@ -551,7 +551,18 @@ processing packets at the required rate.
 The amount of Tx retries on a vhost-user or vhost-user-client interface can be
 shown with::
 
-  $ ovs-vsctl get Interface dpdkvhostclient0 statistics:tx_retries
+  $ ovs-vsctl get Interface dpdkvhostclient0 statistics:netdev_dpdk_tx_retries
+
+When the guest is not able to consume the packets fast enough, the transmit
+queue of the port gets filled up i.e queue runs out of free descriptors.
+This is the most likely reason why dpdk transmit API will fail to send packets
+besides other reasons.
+
+The amount of tx failure drops on a dpdk vhost/physical interface can be
+shown with::
+
+  $ ovs-vsctl get Interface dpdkvhostclient0 \
+                            statistics:netdev_dpdk_tx_failure_drops
 
 vhost-user Dequeue Zero Copy (experimental)
 -------------------------------------------
diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
index 652b57e3b..fd8f9102e 100644
--- a/lib/netdev-dpdk.c
+++ b/lib/netdev-dpdk.c
@@ -174,6 +174,20 @@ static const struct vhost_device_ops virtio_net_device_ops =
     .destroy_connection = destroy_connection,
 };
 
+/* Custom software stats for dpdk ports */
+struct netdev_dpdk_sw_stats {
+    /* No. of retries when unable to transmit. */
+    uint64_t tx_retries;
+    /* Packet drops when unable to transmit; Probably Tx queue is full. */
+    uint64_t tx_failure_drops;
+    /* Packet length greater than device MTU. */
+    uint64_t tx_mtu_exceeded_drops;
+    /* Packet drops in egress policer processing. */
+    uint64_t tx_qos_drops;
+    /* Packet drops in ingress policer processing. */
+    uint64_t rx_qos_drops;
+};
+
 enum { DPDK_RING_SIZE = 256 };
 BUILD_ASSERT_DECL(IS_POW2(DPDK_RING_SIZE));
 enum { DRAIN_TSC = 200000ULL };
@@ -413,11 +427,10 @@ struct netdev_dpdk {
 
     PADDED_MEMBERS(CACHE_LINE_SIZE,
         struct netdev_stats stats;
-        /* Custom stat for retries when unable to transmit. */
-        uint64_t tx_retries;
+        struct netdev_dpdk_sw_stats *sw_stats;
         /* Protects stats */
         rte_spinlock_t stats_lock;
-        /* 4 pad bytes here. */
+        /* 36 pad bytes here. */
     );
 
     PADDED_MEMBERS(CACHE_LINE_SIZE,
@@ -1173,7 +1186,9 @@ common_construct(struct netdev *netdev, dpdk_port_t port_no,
     dev->rte_xstats_ids = NULL;
     dev->rte_xstats_ids_size = 0;
 
-    dev->tx_retries = (dev->type == DPDK_DEV_VHOST) ? 0 : UINT64_MAX;
+    dev->sw_stats = (struct netdev_dpdk_sw_stats *)
+                        xzalloc(sizeof *dev->sw_stats);
+    dev->sw_stats->tx_retries = (dev->type == DPDK_DEV_VHOST) ? 0 : UINT64_MAX;
 
     return 0;
 }
@@ -1359,6 +1374,7 @@ common_destruct(struct netdev_dpdk *dev)
     ovs_list_remove(&dev->list_node);
     free(ovsrcu_get_protected(struct ingress_policer *,
                               &dev->ingress_policer));
+    free(dev->sw_stats);
     ovs_mutex_destroy(&dev->mutex);
 }
 
@@ -2209,6 +2225,7 @@ netdev_dpdk_vhost_rxq_recv(struct netdev_rxq *rxq,
     rte_spinlock_lock(&dev->stats_lock);
     netdev_dpdk_vhost_update_rx_counters(&dev->stats, batch->packets,
                                          nb_rx, dropped);
+    dev->sw_stats->rx_qos_drops += dropped;
     rte_spinlock_unlock(&dev->stats_lock);
 
     batch->count = nb_rx;
@@ -2258,6 +2275,7 @@ netdev_dpdk_rxq_recv(struct netdev_rxq *rxq, struct dp_packet_batch *batch,
     if (OVS_UNLIKELY(dropped)) {
         rte_spinlock_lock(&dev->stats_lock);
         dev->stats.rx_dropped += dropped;
+        dev->sw_stats->rx_qos_drops += dropped;
         rte_spinlock_unlock(&dev->stats_lock);
     }
 
@@ -2341,6 +2359,10 @@ __netdev_dpdk_vhost_send(struct netdev *netdev, int qid,
     struct rte_mbuf **cur_pkts = (struct rte_mbuf **) pkts;
     unsigned int total_pkts = cnt;
     unsigned int dropped = 0;
+    unsigned int tx_failure;
+    unsigned int mtu_drops;
+    unsigned int qos_drops;
+    struct netdev_dpdk_sw_stats *sw_stats = dev->sw_stats;
     int i, retries = 0;
     int max_retries = VHOST_ENQ_RETRY_MIN;
     int vid = netdev_dpdk_get_vid(dev);
@@ -2358,9 +2380,12 @@ __netdev_dpdk_vhost_send(struct netdev *netdev, int qid,
     rte_spinlock_lock(&dev->tx_q[qid].tx_lock);
 
     cnt = netdev_dpdk_filter_packet_len(dev, cur_pkts, cnt);
+    mtu_drops = total_pkts - cnt;
+    qos_drops = cnt;
     /* Check has QoS has been configured for the netdev */
     cnt = netdev_dpdk_qos_run(dev, cur_pkts, cnt, true);
-    dropped = total_pkts - cnt;
+    qos_drops -= cnt;
+    dropped = qos_drops + mtu_drops;
 
     do {
         int vhost_qid = qid * VIRTIO_QNUM + VIRTIO_RXQ;
@@ -2385,12 +2410,16 @@ __netdev_dpdk_vhost_send(struct netdev *netdev, int qid,
         }
     } while (cnt && (retries++ < max_retries));
 
+    tx_failure = cnt;
     rte_spinlock_unlock(&dev->tx_q[qid].tx_lock);
 
     rte_spinlock_lock(&dev->stats_lock);
     netdev_dpdk_vhost_update_tx_counters(&dev->stats, pkts, total_pkts,
                                          cnt + dropped);
-    dev->tx_retries += MIN(retries, max_retries);
+    sw_stats->tx_retries += MIN(retries, max_retries);
+    sw_stats->tx_failure_drops += tx_failure;
+    sw_stats->tx_mtu_exceeded_drops += mtu_drops;
+    sw_stats->tx_qos_drops += qos_drops;
     rte_spinlock_unlock(&dev->stats_lock);
 
 out:
@@ -2415,12 +2444,16 @@ dpdk_do_tx_copy(struct netdev *netdev, int qid, struct dp_packet_batch *batch)
     struct rte_mbuf *pkts[PKT_ARRAY_SIZE];
     uint32_t cnt = batch_cnt;
     uint32_t dropped = 0;
+    uint32_t tx_failure = 0;
+    uint32_t mtu_drops = 0;
+    uint32_t qos_drops = 0;
+    struct netdev_dpdk_sw_stats *sw_stats = dev->sw_stats;
 
     if (dev->type != DPDK_DEV_VHOST) {
         /* Check if QoS has been configured for this netdev. */
         cnt = netdev_dpdk_qos_run(dev, (struct rte_mbuf **) batch->packets,
                                   batch_cnt, false);
-        dropped += batch_cnt - cnt;
+        qos_drops = batch_cnt - cnt;
     }
 
     uint32_t txcnt = 0;
@@ -2433,7 +2466,7 @@ dpdk_do_tx_copy(struct netdev *netdev, int qid, struct dp_packet_batch *batch)
             VLOG_WARN_RL(&rl, "Too big size %u max_packet_len %d",
                          size, dev->max_packet_len);
 
-            dropped++;
+            mtu_drops++;
             continue;
         }
 
@@ -2456,13 +2489,17 @@ dpdk_do_tx_copy(struct netdev *netdev, int qid, struct dp_packet_batch *batch)
             __netdev_dpdk_vhost_send(netdev, qid, (struct dp_packet **) pkts,
                                      txcnt);
         } else {
-            dropped += netdev_dpdk_eth_tx_burst(dev, qid, pkts, txcnt);
+            tx_failure = netdev_dpdk_eth_tx_burst(dev, qid, pkts, txcnt);
         }
     }
 
+    dropped += qos_drops + mtu_drops + tx_failure;
     if (OVS_UNLIKELY(dropped)) {
         rte_spinlock_lock(&dev->stats_lock);
         dev->stats.tx_dropped += dropped;
+        sw_stats->tx_failure_drops += tx_failure;
+        sw_stats->tx_mtu_exceeded_drops += mtu_drops;
+        sw_stats->tx_qos_drops += qos_drops;
         rte_spinlock_unlock(&dev->stats_lock);
     }
 }
@@ -2503,19 +2540,27 @@ netdev_dpdk_send__(struct netdev_dpdk *dev, int qid,
         dpdk_do_tx_copy(netdev, qid, batch);
         dp_packet_delete_batch(batch, true);
     } else {
+        struct netdev_dpdk_sw_stats *sw_stats = dev->sw_stats;
         int tx_cnt, dropped;
+        int tx_failure, mtu_drops, qos_drops;
         int batch_cnt = dp_packet_batch_size(batch);
         struct rte_mbuf **pkts = (struct rte_mbuf **) batch->packets;
 
         tx_cnt = netdev_dpdk_filter_packet_len(dev, pkts, batch_cnt);
+        mtu_drops = batch_cnt - tx_cnt;
+        qos_drops = tx_cnt;
         tx_cnt = netdev_dpdk_qos_run(dev, pkts, tx_cnt, true);
-        dropped = batch_cnt - tx_cnt;
+        qos_drops -= tx_cnt;
 
-        dropped += netdev_dpdk_eth_tx_burst(dev, qid, pkts, tx_cnt);
+        tx_failure = netdev_dpdk_eth_tx_burst(dev, qid, pkts, tx_cnt);
 
+        dropped = tx_failure + mtu_drops + qos_drops;
         if (OVS_UNLIKELY(dropped)) {
             rte_spinlock_lock(&dev->stats_lock);
             dev->stats.tx_dropped += dropped;
+            sw_stats->tx_failure_drops += tx_failure;
+            sw_stats->tx_mtu_exceeded_drops += mtu_drops;
+            sw_stats->tx_qos_drops += qos_drops;
             rte_spinlock_unlock(&dev->stats_lock);
         }
     }
@@ -2826,8 +2871,12 @@ netdev_dpdk_get_sw_custom_stats(const struct netdev *netdev,
     struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
     int i, n;
 
-#define SW_CSTATS \
-    SW_CSTAT(tx_retries)
+#define SW_CSTATS                    \
+    SW_CSTAT(tx_retries)             \
+    SW_CSTAT(tx_failure_drops)       \
+    SW_CSTAT(tx_mtu_exceeded_drops)  \
+    SW_CSTAT(tx_qos_drops)           \
+    SW_CSTAT(rx_qos_drops)
 
 #define SW_CSTAT(NAME) + 1
     custom_stats->size = SW_CSTATS;
@@ -2840,7 +2889,7 @@ netdev_dpdk_get_sw_custom_stats(const struct netdev *netdev,
     rte_spinlock_lock(&dev->stats_lock);
     i = 0;
 #define SW_CSTAT(NAME) \
-    custom_stats->counters[i++].value = dev->NAME;
+    custom_stats->counters[i++].value = dev->sw_stats->NAME;
     SW_CSTATS;
 #undef SW_CSTAT
     rte_spinlock_unlock(&dev->stats_lock);
@@ -2851,8 +2900,8 @@ netdev_dpdk_get_sw_custom_stats(const struct netdev *netdev,
     n = 0;
 #define SW_CSTAT(NAME) \
     if (custom_stats->counters[i].value != UINT64_MAX) {                   \
-        ovs_strlcpy(custom_stats->counters[n].name, #NAME,                 \
-                    NETDEV_CUSTOM_STATS_NAME_SIZE);                        \
+        ovs_strlcpy(custom_stats->counters[n].name,                        \
+                   "netdev_dpdk_"#NAME, NETDEV_CUSTOM_STATS_NAME_SIZE); \
         custom_stats->counters[n].value = custom_stats->counters[i].value; \
         n++;                                                               \
     }                                                                      \
diff --git a/utilities/bugtool/automake.mk b/utilities/bugtool/automake.mk
index 40980b367..dda58e0a1 100644
--- a/utilities/bugtool/automake.mk
+++ b/utilities/bugtool/automake.mk
@@ -22,7 +22,8 @@ bugtool_scripts = \
 	utilities/bugtool/ovs-bugtool-ovs-bridge-datapath-type \
 	utilities/bugtool/ovs-bugtool-ovs-vswitchd-threads-affinity \
 	utilities/bugtool/ovs-bugtool-qos-configs \
-	utilities/bugtool/ovs-bugtool-get-dpdk-nic-numa
+	utilities/bugtool/ovs-bugtool-get-dpdk-nic-numa \
+	utilities/bugtool/ovs-bugtool-get-port-stats
 
 scripts_SCRIPTS += $(bugtool_scripts)
 
diff --git a/utilities/bugtool/ovs-bugtool-get-port-stats b/utilities/bugtool/ovs-bugtool-get-port-stats
new file mode 100755
index 000000000..0fe175e6b
--- /dev/null
+++ b/utilities/bugtool/ovs-bugtool-get-port-stats
@@ -0,0 +1,25 @@
+#! /bin/bash
+
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of version 2.1 of the GNU Lesser General
+# Public License as published by the Free Software Foundation.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# Copyright (C) 2019 Ericsson AB
+
+for bridge in `ovs-vsctl -- --real list-br`
+do
+    echo -e "\nBridge : ${bridge}\n"
+    for iface in `ovs-vsctl list-ifaces ${bridge}`
+    do
+        echo -e "iface : ${iface}"
+        ovs-vsctl get interface ${iface} statistics
+        echo -e "\n"
+    done
+    echo -e "iface : ${bridge}"
+    ovs-vsctl get interface ${bridge} statistics
+done
diff --git a/utilities/bugtool/plugins/network-status/openvswitch.xml b/utilities/bugtool/plugins/network-status/openvswitch.xml
index d39867c6e..8c1ec643e 100644
--- a/utilities/bugtool/plugins/network-status/openvswitch.xml
+++ b/utilities/bugtool/plugins/network-status/openvswitch.xml
@@ -40,4 +40,5 @@
     <command label="ovs-ofctl-dump-groups" filters="ovs">/usr/share/openvswitch/scripts/ovs-bugtool-ovs-ofctl-loop-over-bridges "dump-groups"</command>
     <command label="ovs-ofctl-dump-group-stats" filters="ovs" repeat="2">/usr/share/openvswitch/scripts/ovs-bugtool-ovs-ofctl-loop-over-bridges "dump-group-stats"</command>
     <command label="get_dpdk_nic_numa" filters="ovs">/usr/share/openvswitch/scripts/ovs-bugtool-get-dpdk-nic-numa</command>
+    <command label="get_port_statistics" filters="ovs">/usr/share/openvswitch/scripts/ovs-bugtool-get-port-stats</command>
 </collect>
-- 
2.20.1



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