On Thu, 2012-07-26 at 19:36 +0200, Eric Dumazet wrote:

quoted

On Thu, 2012-07-26 at 19:31 +0200, Eric Dumazet wrote:

quoted

On Thu, 2012-07-26 at 10:18 -0700, Alexander Duyck wrote:

quoted

I tested this patch and it looks like it runs, but still has the same
performance issue.  I did some digging into the annotation for
ip_route_intput_noref and it seems like the issue is that I am hitting
the dst_hold call in  __mkroute_input.

David suggested a percpu cache.

nh_rth_input would be allocated by alloc_percpu(struct dst *)

I can work on this.

Wait a minute, on input we should use the noref trick too.

Something like : (on top of latest David patch)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 7a591aa..d5d2ad1 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c

@@ -1371,8 +1371,7 @@ static void ip_handle_martian_source(struct net_device *dev,
 static int __mkroute_input(struct sk_buff *skb,
                           const struct fib_result *res,
                           struct in_device *in_dev,
-                          __be32 daddr, __be32 saddr, u32 tos,
-                          struct rtable **result)
+                          __be32 daddr, __be32 saddr, u32 tos)
 {
        struct rtable *rth;
        int err;

@@ -1423,7 +1422,7 @@ static int __mkroute_input(struct sk_buff *skb,
                if (!itag) {
                        rth = FIB_RES_NH(*res).nh_rth_input;
                        if (rt_cache_valid(rth)) {
-                               dst_hold(&rth->dst);
+                               skb_dst_set_noref(skb, &rth->dst);
                                goto out;
                        }
                        do_cache = true;

@@ -1451,7 +1450,6 @@ static int __mkroute_input(struct sk_buff *skb,

        rt_set_nexthop(rth, daddr, res, NULL, res->fi, res->type, itag);
 out:
-       *result = rth;
        err = 0;
  cleanup:
        return err;

@@ -1463,21 +1461,13 @@ static int ip_mkroute_input(struct sk_buff *skb,
                            struct in_device *in_dev,
                            __be32 daddr, __be32 saddr, u32 tos)
 {
-       struct rtable *rth = NULL;
-       int err;
-
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
        if (res->fi && res->fi->fib_nhs > 1)
                fib_select_multipath(res);
 #endif

        /* create a routing cache entry */
-       err = __mkroute_input(skb, res, in_dev, daddr, saddr, tos, &rth);
-       if (err)
-               return err;
-
-       skb_dst_set(skb, &rth->dst);
-       return 0;
+       return __mkroute_input(skb, res, in_dev, daddr, saddr, tos);
 }

 /*