neigh: optimize neigh_parms_release()

In neigh_parms_release() we loop over all entries to find the entry given in
argument and being able to remove it from the list. By using a double linked
list, we can avoid this loop.

Here are some numbers with 30 000 dummy interfaces configured:

Before the patch:
$ time rmmod dummy
real	2m0.118s
user	0m0.000s
sys	1m50.048s

After the patch:
$ time rmmod dummy
real	1m9.970s
user	0m0.000s
sys	0m47.976s

Suggested-by: Thierry Herbelot <thierry.herbelot@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 15 insertions, 20 deletions

diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index f60558d0254c..dedfb188b1a7 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -69,7 +69,7 @@ struct neigh_parms {
         struct net *net;
 #endif
         struct net_device *dev;
-        struct neigh_parms *next;
+        struct list_head list;
         int     (*neigh_setup)(struct neighbour *);
         void    (*neigh_cleanup)(struct neighbour *);
         struct neigh_table *tbl;
@@ -203,6 +203,7 @@ struct neigh_table {
         void                    (*proxy_redo)(struct sk_buff *skb);
         char                    *id;
         struct neigh_parms      parms;
+        struct list_head        parms_list;
         int                     gc_interval;
         int                     gc_thresh1;
         int                     gc_thresh2;
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index ef31fef25e5a..edd04116ecb7 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -773,7 +773,7 @@ static void neigh_periodic_work(struct work_struct *work)
         if (time_after(jiffies, tbl->last_rand + 300 * HZ)) {
                 struct neigh_parms *p;
                 tbl->last_rand = jiffies;
-                for (p = &tbl->parms; p; p = p->next)
+                list_for_each_entry(p, &tbl->parms_list, list)
                         p->reachable_time =
                                 neigh_rand_reach_time(NEIGH_VAR(p, BASE_REACHABLE_TIME));
         }
@@ -1446,7 +1446,7 @@ static inline struct neigh_parms *lookup_neigh_parms(struct neigh_table *tbl,
 {
         struct neigh_parms *p;
 
-        for (p = &tbl->parms; p; p = p->next) {
+        list_for_each_entry(p, &tbl->parms_list, list) {
                 if ((p->dev && p->dev->ifindex == ifindex && net_eq(neigh_parms_net(p), net)) ||
                     (!p->dev && !ifindex && net_eq(net, &init_net)))
                         return p;
@@ -1481,8 +1481,7 @@ struct neigh_parms *neigh_parms_alloc(struct net_device *dev,
                 }
 
                 write_lock_bh(&tbl->lock);
-                p->next         = tbl->parms.next;
-                tbl->parms.next = p;
+                list_add(&p->list, &tbl->parms.list);
                 write_unlock_bh(&tbl->lock);
 
                 neigh_parms_data_state_cleanall(p);
@@ -1501,24 +1500,15 @@ static void neigh_rcu_free_parms(struct rcu_head *head)
 
 void neigh_parms_release(struct neigh_table *tbl, struct neigh_parms *parms)
 {
-        struct neigh_parms **p;
-
         if (!parms || parms == &tbl->parms)
                 return;
         write_lock_bh(&tbl->lock);
-        for (p = &tbl->parms.next; *p; p = &(*p)->next) {
-                if (*p == parms) {
-                        *p = parms->next;
-                        parms->dead = 1;
-                        write_unlock_bh(&tbl->lock);
-                        if (parms->dev)
-                                dev_put(parms->dev);
-                        call_rcu(&parms->rcu_head, neigh_rcu_free_parms);
-                        return;
-                }
-        }
+        list_del(&parms->list);
+        parms->dead = 1;
         write_unlock_bh(&tbl->lock);
-        neigh_dbg(1, "%s: not found\n", __func__);
+        if (parms->dev)
+                dev_put(parms->dev);
+        call_rcu(&parms->rcu_head, neigh_rcu_free_parms);
 }
 EXPORT_SYMBOL(neigh_parms_release);
 
@@ -1535,6 +1525,8 @@ static void neigh_table_init_no_netlink(struct neigh_table *tbl)
         unsigned long now = jiffies;
         unsigned long phsize;
 
+        INIT_LIST_HEAD(&tbl->parms_list);
+        list_add(&tbl->parms.list, &tbl->parms_list);
         write_pnet(&tbl->parms.net, &init_net);
         atomic_set(&tbl->parms.refcnt, 1);
         tbl->parms.reachable_time =
@@ -2154,7 +2146,9 @@ static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
                                        NLM_F_MULTI) <= 0)
                         break;
 
-                for (nidx = 0, p = tbl->parms.next; p; p = p->next) {
+                nidx = 0;
+                p = list_next_entry(&tbl->parms, list);
+                list_for_each_entry_from(p, &tbl->parms_list, list) {
                         if (!net_eq(neigh_parms_net(p), net))
                                 continue;