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ipv4: __mkroute_output() speedup

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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@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2010-09-29 11:53:50 +00:00 • committed by David S. Miller
commit dd28d1a0b5
1 changed files with 15 additions and 18 deletions
Download patch file Download diff file Expand all files Collapse all files

33
net/ipv4/route.c
View file

@ -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,