openvswitch: Move flow table rehashing to flow install.

Rehashing in ovs-workqueue can cause ovs-mutex lock contentions
in case of heavy flow setups where both needs ovs-mutex.  So by
moving rehashing to flow-setup we can eliminate contention.
This also simplify ovs locking and reduces dependence on
workqueue.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>

2 files changed, 13 insertions, 39 deletions

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 2aa13bd7f2b2..2e1a9c24e380 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -60,8 +60,6 @@
 
 
 #define REHASH_FLOW_INTERVAL (10 * 60 * HZ)
-static void rehash_flow_table(struct work_struct *work);
-static DECLARE_DELAYED_WORK(rehash_flow_wq, rehash_flow_table);
 
 int ovs_net_id __read_mostly;
 
@@ -1289,22 +1287,25 @@ static int ovs_flow_cmd_new_or_set(struct sk_buff *skb, struct genl_info *info)
         /* Check if this is a duplicate flow */
         flow = ovs_flow_lookup(table, &key);
         if (!flow) {
+                struct flow_table *new_table = NULL;
                 struct sw_flow_mask *mask_p;
+
                 /* Bail out if we're not allowed to create a new flow. */
                 error = -ENOENT;
                 if (info->genlhdr->cmd == OVS_FLOW_CMD_SET)
                         goto err_unlock_ovs;
 
                 /* Expand table, if necessary, to make room. */
-                if (ovs_flow_tbl_need_to_expand(table)) {
-                        struct flow_table *new_table;
-
+                if (ovs_flow_tbl_need_to_expand(table))
                         new_table = ovs_flow_tbl_expand(table);
-                        if (!IS_ERR(new_table)) {
-                                rcu_assign_pointer(dp->table, new_table);
-                                ovs_flow_tbl_destroy(table, true);
-                                table = ovsl_dereference(dp->table);
-                        }
+                else if (time_after(jiffies, dp->last_rehash + REHASH_FLOW_INTERVAL))
+                        new_table = ovs_flow_tbl_rehash(table);
+
+                if (new_table && !IS_ERR(new_table)) {
+                        rcu_assign_pointer(dp->table, new_table);
+                        ovs_flow_tbl_destroy(table, true);
+                        table = ovsl_dereference(dp->table);
+                        dp->last_rehash = jiffies;
                 }
 
                 /* Allocate flow. */
@@ -2336,32 +2337,6 @@ error:
         return err;
 }
 
-static void rehash_flow_table(struct work_struct *work)
-{
-        struct datapath *dp;
-        struct net *net;
-
-        ovs_lock();
-        rtnl_lock();
-        for_each_net(net) {
-                struct ovs_net *ovs_net = net_generic(net, ovs_net_id);
-
-                list_for_each_entry(dp, &ovs_net->dps, list_node) {
-                        struct flow_table *old_table = ovsl_dereference(dp->table);
-                        struct flow_table *new_table;
-
-                        new_table = ovs_flow_tbl_rehash(old_table);
-                        if (!IS_ERR(new_table)) {
-                                rcu_assign_pointer(dp->table, new_table);
-                                ovs_flow_tbl_destroy(old_table, true);
-                        }
-                }
-        }
-        rtnl_unlock();
-        ovs_unlock();
-        schedule_delayed_work(&rehash_flow_wq, REHASH_FLOW_INTERVAL);
-}
-
 static int __net_init ovs_init_net(struct net *net)
 {
         struct ovs_net *ovs_net = net_generic(net, ovs_net_id);
@@ -2419,8 +2394,6 @@ static int __init dp_init(void)
         if (err < 0)
                 goto error_unreg_notifier;
 
-        schedule_delayed_work(&rehash_flow_wq, REHASH_FLOW_INTERVAL);
-
         return 0;
 
 error_unreg_notifier:
@@ -2437,7 +2410,6 @@ error:
 
 static void dp_cleanup(void)
 {
-        cancel_delayed_work_sync(&rehash_flow_wq);
         dp_unregister_genl(ARRAY_SIZE(dp_genl_families));
         unregister_netdevice_notifier(&ovs_dp_device_notifier);
         unregister_pernet_device(&ovs_net_ops);
diff --git a/net/openvswitch/datapath.h b/net/openvswitch/datapath.h
index 4d109c176ef3..2c15541f3b46 100644
--- a/net/openvswitch/datapath.h
+++ b/net/openvswitch/datapath.h
@@ -62,6 +62,7 @@ struct dp_stats_percpu {
  * ovs_mutex and RCU.
  * @stats_percpu: Per-CPU datapath statistics.
  * @net: Reference to net namespace.
+ * @last_rehash: Timestamp of last rehash.
  *
  * Context: See the comment on locking at the top of datapath.c for additional
  * locking information.
@@ -83,6 +84,7 @@ struct datapath {
         /* Network namespace ref. */
         struct net *net;
 #endif
+        unsigned long last_rehash;
 };
 
 /**