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>
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index ba52f39..0f80dfc 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -148,6 +148,13 @@
/* Release a nexthop info record */
+static void free_fib_info_rcu(struct rcu_head *head)
+{
+ struct fib_info *fi = container_of(head, struct fib_info, rcu);
+
+ kfree(fi);
+}
+
void free_fib_info(struct fib_info *fi)
{
if (fi->fib_dead == 0) {
@@ -161,7 +168,7 @@
} endfor_nexthops(fi);
fib_info_cnt--;
release_net(fi->fib_net);
- kfree(fi);
+ call_rcu(&fi->rcu, free_fib_info_rcu);
}
void fib_release_info(struct fib_info *fi)
@@ -553,6 +560,7 @@
nh->nh_scope = RT_SCOPE_LINK;
return 0;
}
+ rcu_read_lock();
{
struct flowi fl = {
.nl_u = {
@@ -568,8 +576,10 @@
if (fl.fl4_scope < RT_SCOPE_LINK)
fl.fl4_scope = RT_SCOPE_LINK;
err = fib_lookup(net, &fl, &res);
- if (err)
+ if (err) {
+ rcu_read_unlock();
return err;
+ }
}
err = -EINVAL;
if (res.type != RTN_UNICAST && res.type != RTN_LOCAL)
@@ -585,7 +595,7 @@
goto out;
err = 0;
out:
- fib_res_put(&res);
+ rcu_read_unlock();
return err;
} else {
struct in_device *in_dev;
@@ -879,7 +889,7 @@
/* Note! fib_semantic_match intentionally uses RCU list functions. */
int fib_semantic_match(struct list_head *head, const struct flowi *flp,
- struct fib_result *res, int prefixlen)
+ struct fib_result *res, int prefixlen, int fib_flags)
{
struct fib_alias *fa;
int nh_sel = 0;
@@ -943,7 +953,8 @@
res->type = fa->fa_type;
res->scope = fa->fa_scope;
res->fi = fa->fa_info;
- atomic_inc(&res->fi->fib_clntref);
+ if (!(fib_flags & FIB_LOOKUP_NOREF))
+ atomic_inc(&res->fi->fib_clntref);
return 0;
}