netdev - [PATCH net-next] ipv6: use DST_NOCOUNT in ip6_rt_pcpu

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Date:   Fri,  8 May 2020 07:34:14 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        David Ahern <dsahern@...nel.org>, Wei Wang <weiwan@...gle.com>,
        "Maciej Żenczykowski" <maze@...gle.com>
Subject: [PATCH net-next] ipv6: use DST_NOCOUNT in ip6_rt_pcpu_alloc()

We currently have to adjust ipv6 route gc_thresh/max_size depending
on number of cpus on a server, this makes very little sense.

If the kernels sets /proc/sys/net/ipv6/route/gc_thresh to 1024
and /proc/sys/net/ipv6/route/max_size to 4096, then we better
not track the percpu dst that our implementation uses.

Only routes not added (directly or indirectly) by the admin
should be tracked and limited.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Martin KaFai Lau <kafai@...com>
Cc: David Ahern <dsahern@...nel.org>
Cc: Wei Wang <weiwan@...gle.com>
Cc: Maciej Żenczykowski <maze@...gle.com>
---
 net/ipv6/route.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index a9072dba00f4fb0b61bce1fc0f44a3a81ba702fa..4292653af533bb641ae8571fffe45b39327d0380 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1377,7 +1377,7 @@ static struct rt6_info *ip6_rt_pcpu_alloc(const struct fib6_result *res)
 
 	rcu_read_lock();
 	dev = ip6_rt_get_dev_rcu(res);
-	pcpu_rt = ip6_dst_alloc(dev_net(dev), dev, flags);
+	pcpu_rt = ip6_dst_alloc(dev_net(dev), dev, flags | DST_NOCOUNT);
 	rcu_read_unlock();
 	if (!pcpu_rt) {
 		fib6_info_release(f6i);
-- 
2.26.2.645.ge9eca65c58-goog