netdev - Re: TSO/GRO/LRO/somethingO breaks LVS on 2.6.36

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Message-ID: <1291863119.2795.29.camel@edumazet-laptop>
Date:	Thu, 09 Dec 2010 03:51:59 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Simon Kirby <sim@...tway.ca>
Cc:	Simon Horman <horms@...ge.net.au>, netdev@...r.kernel.org
Subject: Re: TSO/GRO/LRO/somethingO breaks LVS on 2.6.36

Le mercredi 08 décembre 2010 à 18:35 -0800, Simon Kirby a écrit :

> Right.  So, on 2.6.35, ethtool shows:
> 
> # ethtool -k eth1
> Offload parameters for eth1:
> rx-checksumming: on
> tx-checksumming: on
> scatter-gather: on
> tcp segmentation offload: on
> udp fragmentation offload: off
> generic segmentation offload: on
> large receive offload: off
> 
> # ethtool -k eth1.39
> Offload parameters for eth1.39:
> rx-checksumming: on
> tx-checksumming: off
> scatter-gather: off
> tcp segmentation offload: off
> udp fragmentation offload: off
> generic segmentation offload: off
> large receive offload: off
> 
> On 2.6.36, ethtool shows:
> 
> # ethtool -k eth1
> Offload parameters for eth1:
> rx-checksumming: on
> tx-checksumming: on
> scatter-gather: on
> tcp segmentation offload: on
> udp fragmentation offload: off
> generic segmentation offload: on
> large receive offload: off
> 
> # ethtool -k eth1.39
> Offload parameters for eth1.39:
> rx-checksumming: on
> tx-checksumming: on
> scatter-gather: on
> tcp segmentation offload: on
> udp fragmentation offload: off
> generic segmentation offload: on
> large receive offload: off
> 
> And if I set it with ethtool -K eth1.39 gso off; ethtool -K eth1 gso off,
> it says "off", but I still see merged frames, as verified with an nc <
> /dev/zero and tcpdump -i any -n 'length > 1500'.
> 


Yep, but you also have "tso on" by default on 2.6.36 and eth1.39 (vlan)

> > I will prepare a backport of the "ipvs: allow transmit of GRO aggregated
> > skbs" patch to v2.6.36 and post it shortly.  Testing to see if that
> > resolves the problem that you are seeing would probably be a good start.
> 
> I can test this in our case, and it should specifically work on the
> servers we were seeing the problem on, but it still needs some
> complicated logic to be safe for all cases (like when LVS decides to
> route out an interface without GRO).  Anyway, thanks!
> 
> Simon-


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