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

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Date:	Thu, 11 Feb 2016 15:59:25 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Paolo Abeni <pabeni@...hat.com>, 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: Re: [PATCH net-next 7/7] net/ipv4: add dst cache support for gre
 lwtunnels

Hello.

On 2/11/2016 1:12 PM, Paolo Abeni wrote:

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

    Gives.

> 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;

    DaveM prefers the declarations "sorted" from longest to shortest.

>
>   	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;
> +

    Empty line hardly needed here.

> +	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);
>

MBR, Sergei