netdev - Re: [PATCH v2 net] macvlan: Add support for 'always

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Date:	Mon, 03 Mar 2014 15:49:40 -0800
From:	Ben Greear <greearb@...delatech.com>
To:	Vlad Yasevich <vyasevic@...hat.com>
CC:	netdev@...r.kernel.org, Florian Westphal <fw@...len.de>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Jason Wang <jasowang@...hat.com>,
	"Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH v2 net] macvlan: Add support for 'always_on' offload features

On 03/03/2014 12:33 PM, Vlad Yasevich wrote:
> Macvlan currently inherits all of its features from the lower
> device.  When lower device disables offload support, this causes
> macvlan to disable offload support as well.  This causes
> performance regression when using macvlan/macvtap in bridge
> mode.
> 
> It can be easily demonstrated by creating 2 namespaces using
> macvlan in bridge mode and running netperf between them:
> 
> MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.0.0.1 () port 0 AF_INET
> Recv   Send    Send
> Socket Socket  Message  Elapsed
> Size   Size    Size     Time     Throughput
> bytes  bytes   bytes    secs.    10^6bits/sec
> 
>  87380  16384  16384    20.00    1204.61
> 
> To restore the performance, we add software offload features
> to the list of "always_on" features for macvlan.  This way
> when a namespace or a guest using macvtap initially sends a
> packet, this packet will not be segmented at macvlan level.
> It will only be segmented when macvlan sends the packet
> to the lower device.

If users specifically disable the offload features on the macvlan using ethtool,
will they be turned off?  If not, then I think that logic should
be kept somehow?

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

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