[PATCH RFC net 0/2] ipv6: Avoid restarting fib6_lookup() for RTF_CACHE hit

[PATCH RFC net 0/2] ipv6: Avoid restarting fib6_lookup() for RTF_CACHE hit

[Martin KaFai Lau]

I am trying to understand why there is a need to restart fib6_lookup() after
getting rt with RTF_CACHE.

I have adapted the davem's udpflood test
(https://git.kernel.org/pub/scm/linux/kernel/git/davem/net_test_tools.git) to
support IPv6 and here is the result:

#root > time ./udpflood -l 20000000 -c 250 2401:db00:face:face::2

Before:
real    0m33.224s
user    0m2.941s
sys     0m30.232s

After:
real    0m31.517s
user    0m2.938s
sys     0m28.536s

[PATCH RFC net 1/2] ipv6: Remove the net->ipv6.ip6_null_entry check

[Martin KaFai Lau]

The above BACKTRACK have already caught the rt == net->ipv6.ip6_null_entry case
---
 net/ipv6/route.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index bafde82..d53dc4f 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -936,8 +936,7 @@ restart:
 	if (rt->rt6i_nsiblings)
 		rt = rt6_multipath_select(rt, fl6, oif, strict | reachable);
 	BACKTRACK(net, &fl6->saddr);
-	if (rt == net->ipv6.ip6_null_entry ||
-	    rt->rt6i_flags & RTF_CACHE)
+	if (rt->rt6i_flags & RTF_CACHE)
 		goto out;
 
 	dst_hold(&rt->dst);
-- 
1.8.1

[PATCH RFC net 2/2] ipv6: Avoid restarting fib6_lookup() for RTF_CACHE hit case

[Martin KaFai Lau]

When there is a RTF_CACHE hit, no need to redo fib6_lookup()
with reachable=0.
---
 net/ipv6/route.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index d53dc4f..e40b5dc 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -937,7 +937,7 @@ restart:
 		rt = rt6_multipath_select(rt, fl6, oif, strict | reachable);
 	BACKTRACK(net, &fl6->saddr);
 	if (rt->rt6i_flags & RTF_CACHE)
-		goto out;
+		goto out1;
 
 	dst_hold(&rt->dst);
 	read_unlock_bh(&table->tb6_lock);
@@ -974,6 +974,7 @@ out:
 		reachable = 0;
 		goto restart_2;
 	}
+out1:
 	dst_hold(&rt->dst);
 	read_unlock_bh(&table->tb6_lock);
 out2:
-- 
1.8.1

Re: [PATCH RFC net 0/2] ipv6: Avoid restarting fib6_lookup() for RTF_CACHE hit

[David Miller]

From: Martin KaFai Lau <kafai@fb.com>
Date: Fri, 3 Oct 2014 15:12:10 -0700

> I am trying to understand why there is a need to restart fib6_lookup() after
> getting rt with RTF_CACHE.
> 
> I have adapted the davem's udpflood test
> (https://git.kernel.org/pub/scm/linux/kernel/git/davem/net_test_tools.git) to
> support IPv6 and here is the result:
> 
> #root > time ./udpflood -l 20000000 -c 250 2401:db00:face:face::2
> 
> Before:
> real    0m33.224s
> user    0m2.941s
> sys     0m30.232s
> 
> After:
> real    0m31.517s
> user    0m2.938s
> sys     0m28.536s

If you are serious about seeing these patches integrated, you must
freshly repost this series and provide a proper "Signed-off-by: " tag
for yourself in the commit messages.