bfd/cfm: Check status change before update status to database.

This commit adds boolean flag in bfd/cfm module for checking
status change.  If there is no status change, the current
update to OVS database will skip the bfd/cfm session.

In the experiment with 5K bfd sessions, when one session is
flapping at rate of every 0.3 second, this patch reduces the
cpu utilization of the ovs-vswitchd thread from 13 to 6.

Signed-off-by: Alex Wang <alexw@nicira.com>
Acked-by: Joe Stringer <joestringer@nicira.com>

4 files changed, 64 insertions, 5 deletions

diff --git a/lib/bfd.c b/lib/bfd.c
index 8bfe38584..e3e3ae5f1 100644
--- a/lib/bfd.c
+++ b/lib/bfd.c
@@ -213,6 +213,10 @@ struct bfd {
     long long int decay_detect_time; /* Decay detection time. */
 
     uint64_t flap_count;          /* Counts bfd forwarding flaps. */
+
+    /* True when the variables returned by bfd_get_status() are changed
+     * since last check. */
+    bool status_changed;
 };
 
 static struct ovs_mutex mutex = OVS_MUTEX_INITIALIZER;
@@ -240,6 +244,7 @@ static void bfd_put_details(struct ds *, const struct bfd *)
 static uint64_t bfd_rx_packets(const struct bfd *) OVS_REQUIRES(mutex);
 static void bfd_try_decay(struct bfd *) OVS_REQUIRES(mutex);
 static void bfd_decay_update(struct bfd *) OVS_REQUIRES(mutex);
+static void bfd_status_changed(struct bfd *) OVS_REQUIRES(mutex);
 
 static void bfd_forwarding_if_rx_update(struct bfd *) OVS_REQUIRES(mutex);
 static void bfd_unixctl_show(struct unixctl_conn *, int argc,
@@ -279,6 +284,20 @@ bfd_account_rx(struct bfd *bfd, const struct dpif_flow_stats *stats)
     }
 }
 
+/* Returns and resets the 'bfd->status_changed'. */
+bool
+bfd_check_status_change(struct bfd *bfd) OVS_EXCLUDED(mutex)
+{
+    bool ret;
+
+    ovs_mutex_lock(&mutex);
+    ret = bfd->status_changed;
+    bfd->status_changed = false;
+    ovs_mutex_unlock(&mutex);
+
+    return ret;
+}
+
 /* Returns a 'smap' of key value pairs representing the status of 'bfd'
  * intended for the OVS database. */
 void
@@ -749,7 +768,7 @@ bfd_process_packet(struct bfd *bfd, const struct flow *flow,
     }
 
     if (bfd->rmt_state != rmt_state) {
-        seq_change(connectivity_seq_get());
+        bfd_status_changed(bfd);
     }
 
     bfd->rmt_disc = ntohl(msg->my_disc);
@@ -872,7 +891,7 @@ bfd_forwarding__(struct bfd *bfd) OVS_REQUIRES(mutex)
                             && bfd->rmt_diag != DIAG_RCPATH_DOWN;
     if (bfd->last_forwarding != last_forwarding) {
         bfd->flap_count++;
-        seq_change(connectivity_seq_get());
+        bfd_status_changed(bfd);
     }
     return bfd->last_forwarding;
 }
@@ -1085,7 +1104,7 @@ bfd_set_state(struct bfd *bfd, enum state state, enum diag diag)
             bfd_decay_update(bfd);
         }
 
-        seq_change(connectivity_seq_get());
+        bfd_status_changed(bfd);
     }
 }
 
@@ -1132,6 +1151,14 @@ bfd_decay_update(struct bfd * bfd) OVS_REQUIRES(mutex)
     bfd->decay_detect_time = MAX(bfd->decay_min_rx, 2000) + time_msec();
 }
 
+/* Records the status change and changes the global connectivity seq. */
+static void
+bfd_status_changed(struct bfd *bfd) OVS_REQUIRES(mutex)
+{
+    seq_change(connectivity_seq_get());
+    bfd->status_changed = true;
+}
+
 static void
 bfd_forwarding_if_rx_update(struct bfd *bfd) OVS_REQUIRES(mutex)
 {
@@ -1279,9 +1306,11 @@ bfd_unixctl_set_forwarding_override(struct unixctl_conn *conn, int argc,
             goto out;
         }
         bfd->forwarding_override = forwarding_override;
+        bfd_status_changed(bfd);
     } else {
         HMAP_FOR_EACH (bfd, node, all_bfds) {
             bfd->forwarding_override = forwarding_override;
+            bfd_status_changed(bfd);
         }
     }
 
diff --git a/lib/bfd.h b/lib/bfd.h
index 4e7d4cb46..039b4dd96 100644
--- a/lib/bfd.h
+++ b/lib/bfd.h
@@ -49,6 +49,7 @@ void bfd_unref(struct bfd *);
 
 void bfd_account_rx(struct bfd *, const struct dpif_flow_stats *);
 bool bfd_forwarding(struct bfd *);
+bool bfd_check_status_change(struct bfd *);
 void bfd_get_status(const struct bfd *, struct smap *);
 void bfd_set_netdev(struct bfd *, const struct netdev *);
 long long int bfd_wake_time(const struct bfd *);
diff --git a/lib/cfm.c b/lib/cfm.c
index ce0c471e3..6a173a709 100644
--- a/lib/cfm.c
+++ b/lib/cfm.c
@@ -133,6 +133,10 @@ struct cfm {
     struct ovs_refcount ref_cnt;
 
     uint64_t flap_count;       /* Count the flaps since boot. */
+
+    /* True when the variables returned by cfm_get_*() are changed
+     * since last check. */
+    bool status_changed;
 };
 
 /* Remote MPs represent foreign network entities that are configured to have
@@ -343,6 +347,7 @@ cfm_create(const struct netdev *netdev) OVS_EXCLUDED(mutex)
     cfm_generate_maid(cfm);
     hmap_insert(all_cfms, &cfm->hmap_node, hash_string(cfm->name, 0));
     ovs_mutex_unlock(&mutex);
+
     return cfm;
 }
 
@@ -385,6 +390,14 @@ cfm_ref(const struct cfm *cfm_)
     return cfm;
 }
 
+/* Records the status change and changes the global connectivity seq. */
+static void
+cfm_status_changed(struct cfm *cfm) OVS_REQUIRES(mutex)
+{
+    seq_change(connectivity_seq_get());
+    cfm->status_changed = true;
+}
+
 /* Should be run periodically to update fault statistics messages. */
 void
 cfm_run(struct cfm *cfm) OVS_EXCLUDED(mutex)
@@ -510,7 +523,7 @@ cfm_run(struct cfm *cfm) OVS_EXCLUDED(mutex)
             || (old_rmps_array_len != cfm->rmps_array_len || old_rmps_deleted)
             || old_cfm_fault != cfm->fault
             || old_flap_count != cfm->flap_count) {
-            seq_change(connectivity_seq_get());
+            cfm_status_changed(cfm);
         }
 
         cfm->booted = true;
@@ -836,6 +849,20 @@ out:
     ovs_mutex_unlock(&mutex);
 }
 
+/* Returns and resets the 'cfm->status_changed'. */
+bool
+cfm_check_status_change(struct cfm *cfm) OVS_EXCLUDED(mutex)
+{
+    bool ret;
+
+    ovs_mutex_lock(&mutex);
+    ret = cfm->status_changed;
+    cfm->status_changed = false;
+    ovs_mutex_unlock(&mutex);
+
+    return ret;
+}
+
 static int
 cfm_get_fault__(const struct cfm *cfm) OVS_REQUIRES(mutex)
 {
@@ -1029,13 +1056,14 @@ cfm_unixctl_set_fault(struct unixctl_conn *conn, int argc, const char *argv[],
             goto out;
         }
         cfm->fault_override = fault_override;
+        cfm_status_changed(cfm);
     } else {
         HMAP_FOR_EACH (cfm, hmap_node, all_cfms) {
             cfm->fault_override = fault_override;
+            cfm_status_changed(cfm);
         }
     }
 
-    seq_change(connectivity_seq_get());
     unixctl_command_reply(conn, "OK");
 
 out:
diff --git a/lib/cfm.h b/lib/cfm.h
index 4213eb538..13fdc60a6 100644
--- a/lib/cfm.h
+++ b/lib/cfm.h
@@ -76,6 +76,7 @@ void cfm_set_netdev(struct cfm *, const struct netdev *);
 bool cfm_should_process_flow(const struct cfm *cfm, const struct flow *,
                              struct flow_wildcards *);
 void cfm_process_heartbeat(struct cfm *, const struct ofpbuf *packet);
+bool cfm_check_status_change(struct cfm *);
 int cfm_get_fault(const struct cfm *);
 uint64_t cfm_get_flap_count(const struct cfm *);
 int cfm_get_health(const struct cfm *);