netdev - Re: [net-next PATCH 2/2] tuntap: initialize vlan

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Date:	Thu, 11 Apr 2013 12:55:31 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [net-next PATCH 2/2] tuntap: initialize vlan_features

On Thu, Apr 11, 2013 at 05:32:22PM +0800, Jason Wang wrote:
> The vlan_features was zero which prevents vlan GSO packets to be transmitted to
> userspace. This is suboptimal so enable this by initialize vlan_features for
> tuntap.
> 
> Netperf shows better performance of guest receiving since vlan TSO works for
> tuntap:
> 
> before:
> netperf -H 192.168.5.4
> MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.5.4 ()
> port 0 AF_INET : demo
> Recv   Send    Send
> Socket Socket  Message  Elapsed
> Size   Size    Size     Time     Throughput
> bytes  bytes   bytes    secs.    10^6bits/sec
> 
>  87380  16384  16384    10.01    2786.67
> 
> after:
> netperf -H 192.168.5.4
> MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.5.4 ()
> port 0 AF_INET : demo
> Recv   Send    Send
> Socket Socket  Message  Elapsed
> Size   Size    Size     Time     Throughput
> bytes  bytes   bytes    secs.    10^6bits/sec
> 
>  87380  16384  16384    10.00    8085.49
> 
> Signed-off-by: Jason Wang <jasowang@...hat.com>

Acked-by: Michael S. Tsirkin <mst@...hat.com>

> ---
>  drivers/net/tun.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 29538e6..316c759 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1656,6 +1656,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
>  		dev->hw_features = NETIF_F_SG | NETIF_F_FRAGLIST |
>  			TUN_USER_FEATURES;
>  		dev->features = dev->hw_features;
> +		dev->vlan_features = dev->features;
>  
>  		INIT_LIST_HEAD(&tun->disabled);
>  		err = tun_attach(tun, file);
> -- 
> 1.7.1
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