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Date: Wed, 29 Sep 2010 23:53:50 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next] ipv4: __mkroute_output() speedup
While doing stress tests with a disabled IP route cache, I found
__mkroute_output() was touching three times in_device atomic refcount.
Use RCU to touch it once to reduce cache line ping pongs.
Before patch
time to perform the test
real 1m42.009s
user 0m12.545s
sys 25m0.726s
Profile :
16109.00 26.4% ip_route_output_slow vmlinux
7434.00 12.2% dst_destroy vmlinux
3280.00 5.4% fib_rules_lookup vmlinux
3252.00 5.3% fib_semantic_match vmlinux
2622.00 4.3% fib_table_lookup vmlinux
2535.00 4.1% dst_alloc vmlinux
1750.00 2.9% _raw_read_lock vmlinux
1532.00 2.5% rt_set_nexthop vmlinux
After patch
real 1m36.503s
user 0m12.977s
sys 23m25.608s
14234.00 22.4% ip_route_output_slow vmlinux
8717.00 13.7% dst_destroy vmlinux
4052.00 6.4% fib_rules_lookup vmlinux
3951.00 6.2% fib_semantic_match vmlinux
3191.00 5.0% dst_alloc vmlinux
1764.00 2.8% fib_table_lookup vmlinux
1692.00 2.7% _raw_read_lock vmlinux
1605.00 2.5% rt_set_nexthop vmlinux
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
net/ipv4/route.c | 33 +++++++++++++++------------------
1 file changed, 15 insertions(+), 18 deletions(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 98beda4..ea89500 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2358,9 +2358,8 @@ static int __mkroute_output(struct rtable **result,
struct rtable *rth;
struct in_device *in_dev;
u32 tos = RT_FL_TOS(oldflp);
- int err = 0;
- if (ipv4_is_loopback(fl->fl4_src) && !(dev_out->flags&IFF_LOOPBACK))
+ if (ipv4_is_loopback(fl->fl4_src) && !(dev_out->flags & IFF_LOOPBACK))
return -EINVAL;
if (fl->fl4_dst == htonl(0xFFFFFFFF))
@@ -2373,11 +2372,12 @@ static int __mkroute_output(struct rtable **result,
if (dev_out->flags & IFF_LOOPBACK)
flags |= RTCF_LOCAL;
- /* get work reference to inet device */
- in_dev = in_dev_get(dev_out);
- if (!in_dev)
+ rcu_read_lock();
+ in_dev = __in_dev_get_rcu(dev_out);
+ if (!in_dev) {
+ rcu_read_unlock();
return -EINVAL;
-
+ }
if (res->type == RTN_BROADCAST) {
flags |= RTCF_BROADCAST | RTCF_LOCAL;
if (res->fi) {
@@ -2385,13 +2385,13 @@ static int __mkroute_output(struct rtable **result,
res->fi = NULL;
}
} else if (res->type == RTN_MULTICAST) {
- flags |= RTCF_MULTICAST|RTCF_LOCAL;
+ flags |= RTCF_MULTICAST | RTCF_LOCAL;
if (!ip_check_mc(in_dev, oldflp->fl4_dst, oldflp->fl4_src,
oldflp->proto))
flags &= ~RTCF_LOCAL;
/* If multicast route do not exist use
- default one, but do not gateway in this case.
- Yes, it is hack.
+ * default one, but do not gateway in this case.
+ * Yes, it is hack.
*/
if (res->fi && res->prefixlen < 4) {
fib_info_put(res->fi);
@@ -2402,9 +2402,12 @@ static int __mkroute_output(struct rtable **result,
rth = dst_alloc(&ipv4_dst_ops);
if (!rth) {
- err = -ENOBUFS;
- goto cleanup;
+ rcu_read_unlock();
+ return -ENOBUFS;
}
+ in_dev_hold(in_dev);
+ rcu_read_unlock();
+ rth->idev = in_dev;
atomic_set(&rth->dst.__refcnt, 1);
rth->dst.flags= DST_HOST;
@@ -2425,7 +2428,6 @@ static int __mkroute_output(struct rtable **result,
cache entry */
rth->dst.dev = dev_out;
dev_hold(dev_out);
- rth->idev = in_dev_get(dev_out);
rth->rt_gateway = fl->fl4_dst;
rth->rt_spec_dst= fl->fl4_src;
@@ -2460,13 +2462,8 @@ static int __mkroute_output(struct rtable **result,
rt_set_nexthop(rth, res, 0);
rth->rt_flags = flags;
-
*result = rth;
- cleanup:
- /* release work reference to inet device */
- in_dev_put(in_dev);
-
- return err;
+ return 0;
}
static int ip_mkroute_output(struct rtable **rp,
--
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