netdev - [PATCH net-next 7/7] net/ipv4: add dst cache support for gre lwtunnels

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Date:	Thu, 11 Feb 2016 11:12:03 +0100
From:	Paolo Abeni <pabeni@...hat.com>
To:	netdev@...r.kernel.org
Cc:	"David S. Miller" <davem@...emloft.net>,
	Thomas Graf <tgraf@...g.ch>,
	Pravin B Shelar <pshelar@...ira.com>,
	Jiri Benc <jbenc@...hat.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Tom Herbert <therbert@...gle.com>
Subject: [PATCH net-next 7/7] net/ipv4: add dst cache support for gre lwtunnels

In case of UDP traffic with datagram length below MTU this
give about 4% performance increase

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Suggested-and-acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
 net/ipv4/ip_gre.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 7c51c4e..be6f3f6 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -524,6 +524,7 @@ static void gre_fb_xmit(struct sk_buff *skb, struct net_device *dev)
 	int tunnel_hlen;
 	__be16 df, flags;
 	int err;
+	bool use_cache;
 
 	tun_info = skb_tunnel_info(skb);
 	if (unlikely(!tun_info || !(tun_info->mode & IP_TUNNEL_INFO_TX) ||
@@ -531,9 +532,19 @@ static void gre_fb_xmit(struct sk_buff *skb, struct net_device *dev)
 		goto err_free_skb;
 
 	key = &tun_info->key;
-	rt = gre_get_rt(skb, dev, &fl, key);
-	if (IS_ERR(rt))
-		goto err_free_skb;
+
+	use_cache = !skb->mark && tun_info->dst_cache;
+	rt = use_cache ? dst_cache_get_ip4(tun_info->dst_cache, &fl.saddr) :
+			 NULL;
+
+	if (!rt) {
+		rt = gre_get_rt(skb, dev, &fl, key);
+		if (IS_ERR(rt))
+			goto err_free_skb;
+		if (use_cache)
+			dst_cache_set_ip4(tun_info->dst_cache, &rt->dst,
+					  fl.saddr);
+	}
 
 	tunnel_hlen = ip_gre_calc_hlen(key->tun_flags);
 
-- 
1.8.3.1