netdev - Re: TUN device performance regression

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Date:	Mon, 14 Apr 2014 16:51:47 +0200
From:	Martin Filip <nexus+kernel@...ula.net>
To:	Vlad Yasevich <vyasevich@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: TUN device performance regression

Vlad Yasevich píše v Po 14. 04. 2014 v 10:43 -0400:
> On 04/14/2014 07:42 AM, Martin Filip wrote:
> >> Hello,
> >>
> >> I've noticed significant TUN device performance drop between 3.13 and
> >> 3.14 kernels, problem seems to persist until current git version.
> >>
> >> With good kernel I can achieve full 100mbps through openvpn without any
> >> problem, with problematic kernel TX performance drops down to ~50kbps.
> >>
> >> According to git bisect it seems that root of all evil is commit
> >> 53d6471cef17262d3ad1c7ce8982a234244f68ec.
> >>
> >> I can confirm that performance is great again with current kernel when I
> >> revert this one.
> >>
> > I've forgot to mention kernel bug:
> > https://bugzilla.kernel.org/show_bug.cgi?id=74051
> >
> 
> Could you please try this patch.
> 
> ---
>  net/core/dev.c      | 2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 45fa2f1..6088927 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -2289,7 +2289,7 @@ EXPORT_SYMBOL(skb_checksum_help);
>  __be16 skb_network_protocol(struct sk_buff *skb, int *depth)
>  {
>  	__be16 type = skb->protocol;
> -	int vlan_depth = ETH_HLEN;
> +	int vlan_depth = skb->mac_len;
> 
>  	/* Tunnel gso handlers can set protocol to ethernet. */
>  	if (type == htons(ETH_P_TEB)) {

Hello,

thank you for your quick response. This seems to fix the problem, my
test case worked fine with it!

-- 
Martin Filip
e-mail: nexus@...ula.net
jabberID: nexus@...ula.net
http://www.smoula.net


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