fib: RCU conversion of fib_lookup()

fib_lookup() converted to be called in RCU protected context, no
reference taken and released on a contended cache line (fib_clntref)

fib_table_lookup() and fib_semantic_match() get an additional parameter.

struct fib_info gets an rcu_head field, and is freed after an rcu grace
period.

Stress test :
(Sending 160.000.000 UDP frames on same neighbour,
IP route cache disabled, dual E5540 @2.53GHz,
32bit kernel, FIB_HASH) (about same results for FIB_TRIE)

Before patch :

real	1m31.199s
user	0m13.761s
sys	23m24.780s

After patch:

real	1m5.375s
user	0m14.997s
sys	15m50.115s

Before patch Profile :

13044.00 15.4% __ip_route_output_key vmlinux
 8438.00 10.0% dst_destroy           vmlinux
 5983.00  7.1% fib_semantic_match    vmlinux
 5410.00  6.4% fib_rules_lookup      vmlinux
 4803.00  5.7% neigh_lookup          vmlinux
 4420.00  5.2% _raw_spin_lock        vmlinux
 3883.00  4.6% rt_set_nexthop        vmlinux
 3261.00  3.9% _raw_read_lock        vmlinux
 2794.00  3.3% fib_table_lookup      vmlinux
 2374.00  2.8% neigh_resolve_output  vmlinux
 2153.00  2.5% dst_alloc             vmlinux
 1502.00  1.8% _raw_read_lock_bh     vmlinux
 1484.00  1.8% kmem_cache_alloc      vmlinux
 1407.00  1.7% eth_header            vmlinux
 1406.00  1.7% ipv4_dst_destroy      vmlinux
 1298.00  1.5% __copy_from_user_ll   vmlinux
 1174.00  1.4% dev_queue_xmit        vmlinux
 1000.00  1.2% ip_output             vmlinux

After patch Profile :

13712.00 15.8% dst_destroy             vmlinux
 8548.00  9.9% __ip_route_output_key   vmlinux
 7017.00  8.1% neigh_lookup            vmlinux
 4554.00  5.3% fib_semantic_match      vmlinux
 4067.00  4.7% _raw_read_lock          vmlinux
 3491.00  4.0% dst_alloc               vmlinux
 3186.00  3.7% neigh_resolve_output    vmlinux
 3103.00  3.6% fib_table_lookup        vmlinux
 2098.00  2.4% _raw_read_lock_bh       vmlinux
 2081.00  2.4% kmem_cache_alloc        vmlinux
 2013.00  2.3% _raw_spin_lock          vmlinux
 1763.00  2.0% __copy_from_user_ll     vmlinux
 1763.00  2.0% ip_output               vmlinux
 1761.00  2.0% ipv4_dst_destroy        vmlinux
 1631.00  1.9% eth_header              vmlinux
 1440.00  1.7% _raw_read_unlock_bh     vmlinux

Reference results, if IP route cache is enabled :

real	0m29.718s
user	0m10.845s
sys	7m37.341s

25213.00 29.5% __ip_route_output_key   vmlinux
 9011.00 10.5% dst_release             vmlinux
 4817.00  5.6% ip_push_pending_frames  vmlinux
 4232.00  5.0% ip_finish_output        vmlinux
 3940.00  4.6% udp_sendmsg             vmlinux
 3730.00  4.4% __copy_from_user_ll     vmlinux
 3716.00  4.4% ip_route_output_flow    vmlinux
 2451.00  2.9% __xfrm_lookup           vmlinux
 2221.00  2.6% ip_append_data          vmlinux
 1718.00  2.0% _raw_spin_lock_bh       vmlinux
 1655.00  1.9% __alloc_skb             vmlinux
 1572.00  1.8% sock_wfree              vmlinux
 1345.00  1.6% kfree                   vmlinux

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 6 insertions, 13 deletions

diff --git a/include/net/fib_rules.h b/include/net/fib_rules.h
index ac2fd002812e..106f3097d384 100644
--- a/include/net/fib_rules.h
+++ b/include/net/fib_rules.h
@@ -31,6 +31,8 @@ struct fib_lookup_arg {
 	void			*lookup_ptr;
 	void			*result;
 	struct fib_rule		*rule;
+	int			flags;
+#define FIB_LOOKUP_NOREF	1
 };
 
 struct fib_rules_ops {
diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index c93f94edc610..ba3666d31766 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -86,6 +86,7 @@ struct fib_info {
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 	int			fib_power;
 #endif
+	struct rcu_head		rcu;
 	struct fib_nh		fib_nh[0];
 #define fib_dev		fib_nh[0].nh_dev
 };
@@ -148,7 +149,7 @@ struct fib_table {
 };
 
 extern int fib_table_lookup(struct fib_table *tb, const struct flowi *flp,
-			    struct fib_result *res);
+			    struct fib_result *res, int fib_flags);
 extern int fib_table_insert(struct fib_table *, struct fib_config *);
 extern int fib_table_delete(struct fib_table *, struct fib_config *);
 extern int fib_table_dump(struct fib_table *table, struct sk_buff *skb,
@@ -185,11 +186,11 @@ static inline int fib_lookup(struct net *net, const struct flowi *flp,
 	struct fib_table *table;
 
 	table = fib_get_table(net, RT_TABLE_LOCAL);
-	if (!fib_table_lookup(table, flp, res))
+	if (!fib_table_lookup(table, flp, res, FIB_LOOKUP_NOREF))
 		return 0;
 
 	table = fib_get_table(net, RT_TABLE_MAIN);
-	if (!fib_table_lookup(table, flp, res))
+	if (!fib_table_lookup(table, flp, res, FIB_LOOKUP_NOREF))
 		return 0;
 	return -ENETUNREACH;
 }
@@ -254,16 +255,6 @@ static inline void fib_info_put(struct fib_info *fi)
 		free_fib_info(fi);
 }
 
-static inline void fib_res_put(struct fib_result *res)
-{
-	if (res->fi)
-		fib_info_put(res->fi);
-#ifdef CONFIG_IP_MULTIPLE_TABLES
-	if (res->r)
-		fib_rule_put(res->r);
-#endif
-}
-
 #ifdef CONFIG_PROC_FS
 extern int __net_init  fib_proc_init(struct net *net);
 extern void __net_exit fib_proc_exit(struct net *net);