netdev - Re: [PATCH net v2] gso: Update tunnel segmentation to support Tx checksum offload

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Message-Id: <20130711.121934.1561010582863754480.davem@davemloft.net>
Date:	Thu, 11 Jul 2013 12:19:34 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	alexander.h.duyck@...el.com
Cc:	netdev@...r.kernel.org, stephen@...workplumber.org,
	pshelar@...ira.com, joseph.gasparakis@...el.com,
	eric.dumazet@...il.com, jesse@...ira.com
Subject: Re: [PATCH net v2] gso: Update tunnel segmentation to support Tx
 checksum offload

From: Alexander Duyck <alexander.h.duyck@...el.com>
Date: Wed, 10 Jul 2013 17:05:06 -0700

> This change makes it so that the GRE and VXLAN tunnels can make use of Tx
> checksum offload support provided by some drivers via the hw_enc_features.
> Without this fix enabling GSO means sacrificing Tx checksum offload and
> this actually leads to a performance regression as shown below:
> 
>             Utilization
>             Send
> Throughput  local         GSO
> 10^6bits/s  % S           state
>   6276.51   8.39          enabled
>   7123.52   8.42          disabled
> 
> To resolve this it was necessary to address two items.  First
> netif_skb_features needed to be updated so that it would correctly handle
> the Trans Ether Bridging protocol without impacting the need to check for
> Q-in-Q tagging.  To do this it was necessary to update harmonize_features
> so that it used skb_network_protocol instead of just using the outer
> protocol.
> 
> Second it was necessary to update the GRE and UDP tunnel segmentation
> offloads so that they would reset the encapsulation bit and inner header
> offsets after the offload was complete.
> 
> As a result of this change I have seen the following results on a interface
> with Tx checksum enabled for encapsulated frames:
> 
>             Utilization
>             Send
> Throughput  local         GSO
> 10^6bits/s  % S           state
>   7123.52   8.42          disabled
>   8321.75   5.43          enabled
> 
> v2: Instead of replacing refrence to skb->protocol with
>     skb_network_protocol just replace the protocol reference in
>     harmonize_features to allow for double VLAN tag checks.
> 
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>

Applied, thanks Alexander.
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