dpif-netdev: Use separate threads for forwarding.

For now, we use exactly two threads.  Presumably at some point we will want
to make this configurable.

Signed-off-by: Ben Pfaff <blp@nicira.com>

lib/dpif-netdev.c

@@ -39,6 +39,7 @@
 #include "dynamic-string.h"
 #include "flow.h"
 #include "hmap.h"
+#include "latch.h"
 #include "list.h"
 #include "meta-flow.h"
 #include "netdev.h"
@@ -158,6 +159,11 @@ struct dp_netdev {
     struct ovs_rwlock port_rwlock;
     struct hmap ports OVS_GUARDED;
     struct seq *port_seq;       /* Incremented whenever a port changes. */
+
+    /* Forwarding threads. */
+    struct latch exit_latch;
+    struct dp_forwarder *forwarders;
+    size_t n_forwarders;
 };
 
 static struct dp_netdev_port *dp_netdev_lookup_port(const struct dp_netdev *dp,
@@ -281,6 +287,15 @@ struct dp_netdev_actions *dp_netdev_actions_ref(
     const struct dp_netdev_actions *);
 void dp_netdev_actions_unref(struct dp_netdev_actions *);
 
+/* A thread that receives packets from some ports, looks them up in the flow
+ * table, and executes the actions it finds. */
+struct dp_forwarder {
+    struct dp_netdev *dp;
+    pthread_t thread;
+    char *name;
+    uint32_t min_hash, max_hash;
+};
+
 /* Interface to netdev-based datapath. */
 struct dpif_netdev {
     struct dpif dpif;
@@ -317,6 +332,7 @@ static void dp_netdev_execute_actions(struct dp_netdev *dp,
 static void dp_netdev_port_input(struct dp_netdev *dp, struct ofpbuf *packet,
                                  struct pkt_metadata *)
     OVS_REQ_RDLOCK(dp->port_rwlock);
+static void dp_netdev_set_threads(struct dp_netdev *, int n);
 
 static struct dpif_netdev *
 dpif_netdev_cast(const struct dpif *dpif)
@@ -453,6 +469,7 @@ create_dp_netdev(const char *name, const struct dpif_class *class,
     ovs_rwlock_init(&dp->port_rwlock);
     hmap_init(&dp->ports);
     dp->port_seq = seq_create();
+    latch_init(&dp->exit_latch);
 
     ovs_rwlock_wrlock(&dp->port_rwlock);
     error = do_add_port(dp, name, "internal", ODPP_LOCAL);
@@ -461,6 +478,7 @@ create_dp_netdev(const char *name, const struct dpif_class *class,
         dp_netdev_free(dp);
         return error;
     }
+    dp_netdev_set_threads(dp, 2);
 
     *dpp = dp;
     return 0;
@@ -518,6 +536,9 @@ dp_netdev_free(struct dp_netdev *dp)
 
     shash_find_and_delete(&dp_netdevs, dp->name);
 
+    dp_netdev_set_threads(dp, 0);
+    free(dp->forwarders);
+
     dp_netdev_flow_flush(dp);
     ovs_rwlock_wrlock(&dp->port_rwlock);
     HMAP_FOR_EACH_SAFE (port, next, node, &dp->ports) {
@@ -539,6 +560,7 @@ dp_netdev_free(struct dp_netdev *dp)
     hmap_destroy(&dp->ports);
     atomic_flag_destroy(&dp->destroyed);
     ovs_refcount_destroy(&dp->ref_cnt);
+    latch_destroy(&dp->exit_latch);
     free(CONST_CAST(char *, dp->name));
     free(dp);
 }
@@ -1521,6 +1543,126 @@ dp_netdev_actions_unref(struct dp_netdev_actions *actions)
     }
 }
 
+static void *
+dp_forwarder_main(void *f_)
+{
+    struct dp_forwarder *f = f_;
+    struct dp_netdev *dp = f->dp;
+    struct ofpbuf packet;
+
+    f->name = xasprintf("forwarder_%u", ovsthread_id_self());
+    set_subprogram_name("%s", f->name);
+
+    ofpbuf_init(&packet, 0);
+    while (!latch_is_set(&dp->exit_latch)) {
+        bool received_anything;
+        int i;
+
+        ovs_rwlock_rdlock(&dp->port_rwlock);
+        for (i = 0; i < 50; i++) {
+            struct dp_netdev_port *port;
+
+            received_anything = false;
+            HMAP_FOR_EACH (port, node, &f->dp->ports) {
+                if (port->rx
+                    && port->node.hash >= f->min_hash
+                    && port->node.hash <= f->max_hash) {
+                    int buf_size;
+                    int error;
+                    int mtu;
+
+                    if (netdev_get_mtu(port->netdev, &mtu)) {
+                        mtu = ETH_PAYLOAD_MAX;
+                    }
+                    buf_size = DP_NETDEV_HEADROOM + VLAN_ETH_HEADER_LEN + mtu;
+
+                    ofpbuf_clear(&packet);
+                    ofpbuf_reserve_with_tailroom(&packet, DP_NETDEV_HEADROOM,
+                                                 buf_size);
+
+                    error = netdev_rx_recv(port->rx, &packet);
+                    if (!error) {
+                        struct pkt_metadata md
+                            = PKT_METADATA_INITIALIZER(port->port_no);
+                        dp_netdev_port_input(dp, &packet, &md);
+
+                        received_anything = true;
+                    } else if (error != EAGAIN && error != EOPNOTSUPP) {
+                        static struct vlog_rate_limit rl
+                            = VLOG_RATE_LIMIT_INIT(1, 5);
+
+                        VLOG_ERR_RL(&rl, "error receiving data from %s: %s",
+                                    netdev_get_name(port->netdev),
+                                    ovs_strerror(error));
+                    }
+                }
+            }
+
+            if (!received_anything) {
+                break;
+            }
+        }
+
+        if (received_anything) {
+            poll_immediate_wake();
+        } else {
+            struct dp_netdev_port *port;
+
+            HMAP_FOR_EACH (port, node, &f->dp->ports)
+                if (port->rx
+                    && port->node.hash >= f->min_hash
+                    && port->node.hash <= f->max_hash) {
+                    netdev_rx_wait(port->rx);
+                }
+            seq_wait(dp->port_seq, seq_read(dp->port_seq));
+            latch_wait(&dp->exit_latch);
+        }
+        ovs_rwlock_unlock(&dp->port_rwlock);
+
+        poll_block();
+    }
+    ofpbuf_uninit(&packet);
+
+    free(f->name);
+
+    return NULL;
+}
+
+static void
+dp_netdev_set_threads(struct dp_netdev *dp, int n)
+{
+    int i;
+
+    if (n == dp->n_forwarders) {
+        return;
+    }
+
+    /* Stop existing threads. */
+    latch_set(&dp->exit_latch);
+    for (i = 0; i < dp->n_forwarders; i++) {
+        struct dp_forwarder *f = &dp->forwarders[i];
+
+        xpthread_join(f->thread, NULL);
+    }
+    latch_poll(&dp->exit_latch);
+    free(dp->forwarders);
+
+    /* Start new threads. */
+    dp->forwarders = xmalloc(n * sizeof *dp->forwarders);
+    dp->n_forwarders = n;
+    for (i = 0; i < n; i++) {
+        struct dp_forwarder *f = &dp->forwarders[i];
+
+        f->dp = dp;
+        f->min_hash = UINT32_MAX / n * i;
+        f->max_hash = UINT32_MAX / n * (i + 1) - 1;
+        if (i == n - 1) {
+            f->max_hash = UINT32_MAX;
+        }
+        xpthread_create(&f->thread, NULL, dp_forwarder_main, f);
+    }
+}
+
 static void
 dp_netdev_flow_used(struct dp_netdev_flow *netdev_flow,
                     const struct ofpbuf *packet)
@@ -1564,74 +1706,6 @@ dp_netdev_port_input(struct dp_netdev *dp, struct ofpbuf *packet,
     }
 }
 
-static void
-dpif_netdev_run(struct dpif *dpif)
-{
-    struct dp_netdev_port *port;
-    struct dp_netdev *dp;
-    struct ofpbuf packet;
-
-    dp = get_dp_netdev(dpif);
-    ofpbuf_init(&packet, 0);
-
-    ovs_rwlock_rdlock(&dp->port_rwlock);
-    HMAP_FOR_EACH (port, node, &dp->ports) {
-        int buf_size;
-        int error;
-        int mtu;
-
-        error = netdev_get_mtu(port->netdev, &mtu);
-        if (error) {
-            mtu = ETH_PAYLOAD_MAX;
-        }
-        buf_size = DP_NETDEV_HEADROOM + VLAN_ETH_HEADER_LEN + mtu;
-
-        ofpbuf_clear(&packet);
-        ofpbuf_reserve_with_tailroom(&packet, DP_NETDEV_HEADROOM, buf_size);
-
-        error = port->rx ? netdev_rx_recv(port->rx, &packet) : EOPNOTSUPP;
-        if (!error) {
-            struct pkt_metadata md = PKT_METADATA_INITIALIZER(port->port_no);
-            dp_netdev_port_input(dp, &packet, &md);
-        } else if (error != EAGAIN && error != EOPNOTSUPP) {
-            static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
-
-            VLOG_ERR_RL(&rl, "error receiving data from %s: %s",
-                        netdev_get_name(port->netdev), ovs_strerror(error));
-        }
-    }
-    ovs_rwlock_unlock(&dp->port_rwlock);
-
-    ofpbuf_uninit(&packet);
-}
-
-static void
-dpif_netdev_wait(struct dpif *dpif)
-{
-    struct dp_netdev_port *port;
-
-    /* There is a race here, if thread A calls dpif_netdev_wait(dpif) and
-     * thread B calls dpif_port_add(dpif) or dpif_port_remove(dpif) before
-     * A makes it to poll_block().
-     *
-     * But I think it doesn't matter:
-     *
-     *     - In the dpif_port_add() case, A will not wake up when a packet
-     *       arrives on the new port, but this would also happen if the
-     *       ordering were reversed.
-     *
-     *     - In the dpif_port_remove() case, A might wake up spuriously, but
-     *       that is harmless. */
-
-    ovs_mutex_lock(&dp_netdev_mutex);
-    HMAP_FOR_EACH (port, node, &get_dp_netdev(dpif)->ports) {
-        if (port->rx) {
-            netdev_rx_wait(port->rx);
-        }
-    }
-    ovs_mutex_unlock(&dp_netdev_mutex);
-}
-
 static int
 dp_netdev_output_userspace(struct dp_netdev *dp, struct ofpbuf *packet,
                            int queue_no, const struct flow *flow,
@@ -1754,8 +1828,8 @@ const struct dpif_class dpif_netdev_class = {
     dpif_netdev_open,
     dpif_netdev_close,
     dpif_netdev_destroy,
-    dpif_netdev_run,
+    NULL,                       /* run */
-    dpif_netdev_wait,
+    NULL,                       /* wait */
     dpif_netdev_get_stats,
     dpif_netdev_port_add,
     dpif_netdev_port_del,