ip: speedup /proc/net/rt_cache handling

When scanning route cache hash table, we can avoid taking locks for
empty buckets.  Both /proc/net/rt_cache and NETLINK RTM_GETROUTE
interface are taken into account.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index cca921ea855004f726906a9ed9f24249c7c0592b..71598f64c113b8f1851f0a996948ba7c5efdc328 100644 (file)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -282,6 +282,8 @@ static struct rtable *rt_cache_get_first(struct seq_file *seq)
        struct rtable *r = NULL;
 
        for (st->bucket = rt_hash_mask; st->bucket >= 0; --st->bucket) {
+               if (!rt_hash_table[st->bucket].chain)
+                       continue;
                rcu_read_lock_bh();
                r = rcu_dereference(rt_hash_table[st->bucket].chain);
                while (r) {
@@ -299,11 +301,14 @@ static struct rtable *__rt_cache_get_next(struct seq_file *seq,
                                          struct rtable *r)
 {
        struct rt_cache_iter_state *st = seq->private;
+
        r = r->u.dst.rt_next;
        while (!r) {
                rcu_read_unlock_bh();
-               if (--st->bucket < 0)
-                       break;
+               do {
+                       if (--st->bucket < 0)
+                               return NULL;
+               } while (!rt_hash_table[st->bucket].chain);
                rcu_read_lock_bh();
                r = rt_hash_table[st->bucket].chain;
        }
@@ -2840,7 +2845,9 @@ int ip_rt_dump(struct sk_buff *skb,  struct netlink_callback *cb)
        if (s_h < 0)
                s_h = 0;
        s_idx = idx = cb->args[1];
-       for (h = s_h; h <= rt_hash_mask; h++) {
+       for (h = s_h; h <= rt_hash_mask; h++, s_idx = 0) {
+               if (!rt_hash_table[h].chain)
+                       continue;
                rcu_read_lock_bh();
                for (rt = rcu_dereference(rt_hash_table[h].chain), idx = 0; rt;
                     rt = rcu_dereference(rt->u.dst.rt_next), idx++) {
@@ -2859,7 +2866,6 @@ int ip_rt_dump(struct sk_buff *skb,  struct netlink_callback *cb)
                        dst_release(xchg(&skb->dst, NULL));
                }
                rcu_read_unlock_bh();
-               s_idx = 0;
        }
 
 done: