netdev - Re: [PATCH net] macvlan: Fix performance issues with vlan tagged packets

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Message-Id: <20170515.141749.698049536255759644.davem@davemloft.net>
Date:   Mon, 15 May 2017 14:17:49 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     vyasevich@...il.com
Cc:     netdev@...r.kernel.org, jasowang@...hat.com, mst@...hat.com,
        vyasevic@...hat.com
Subject: Re: [PATCH net] macvlan: Fix performance issues with vlan tagged
 packets

From: Vladislav Yasevich <vyasevich@...il.com>
Date: Thu, 11 May 2017 11:09:52 -0400

> Macvlan always turns on offload features that have sofware
> fallback (NETIF_GSO_SOFTWARE).  This allows much higher guest-guest
> communications over macvtap.
> 
> However, macvtap does not turn on these features for vlan tagged traffic.
> As a result, depending on the HW that mactap is configured on, the
> performance of guest-guest communication over a vlan is very
> inconsistent.  If the HW supports TSO/UFO over vlans, then the
> performance will be fine.  If not, the the performance will suffer
> greatly since the VM may continue using TSO/UFO, and will force the host
> segment the traffic and possibly overlow the macvtap queue.
> 
> This patch adds the always on offloads to vlan_features.  This
> makes sure that any vlan tagged traffic between 2 guest will not
> be segmented needlessly.
> 
> Signed-off-by: Vladislav Yasevich <vyasevic@...hat.com>

Indeed, this makes us more consistent with how we handle non-vlan
features in macvtap.

Applied, thanks.