From dd28d1a0b5ecc0f5512f658b1a8fd38bc4f4c98c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 29 Sep 2010 11:53:50 +0000 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- 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 98beda47bc99..ea895004caf3 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, -- 2.20.1