From: Eric Dumazet <eric.dumazet@gmail.com>
To: Simon Kirby <sim@hostway.ca>
Cc: netdev@vger.kernel.org, Simon Horman <horms@verge.net.au>
Subject: Re: TSO/GRO/LRO/somethingO breaks LVS on 2.6.36
Date: Fri, 03 Dec 2010 12:29:03 +0100 [thread overview]
Message-ID: <1291375743.2897.141.camel@edumazet-laptop> (raw)
In-Reply-To: <20101203103447.GA29714@hostway.ca>
Le vendredi 03 décembre 2010 à 02:34 -0800, Simon Kirby a écrit :
> Hello!
>
> We upgraded some LVS (DR) servers from 2.6.35 to 2.6.36 on tg3 cards
> (partno(BCM95721) rev 4201) with VLAN tags in use, to think that
> everything looked great, but in fact...
>
> LVS was receiving magically-merged TCP packets which it tried to forward
> on to the real server, only to get annoyed at itself for trying to
> forward a packet bigger than the device MTU:
>
> IP A.47376 > B.529: . 175488:176936(1448) ack 1 win 92 <nop,nop,timestamp 52737308 29656081>
> IP A.47376 > B.529: . 176936:179832(2896) ack 1 win 92 <nop,nop,timestamp 52737325 29656098>
> IP B > A: ICMP B unreachable - need to frag (mtu 1500), length 556
>
Hi Simon
This is a tcpdump on A ?
Could you take it also on B ?
tcpdump displays large buffers, but they should be split (of course)
when sent on wire.
> This caused packet loss for any merged frames, which caused abysmal
> performance for uploads via the LVS server. Local performance to or
> from the box is still fine, because the stack doesn't care, only the
> forwarding part of LVS is running into the problem.
>
> Furthermore, disabling _everything_ reported by ethtool -k doesn't seem
> to change the result, even if I down/up the interface after, and even if
> I try on every single interface including the VLANned ones. This seems
> to be another bug. Reverting to 2.6.35 makes it all work again.
>
> Possibly related to commit 7fe876af921d1d2bc8353e0062c10ff35e902653
>
> So how should this be fixed? Should LVS be taught to fragment, or must
> we disable the merging in this case? It seems like it would work well if
> the sending side could do the same offload in reverse, but I'm not sure
> if that would be possible.
>
> Simon-
I believe Simon Horman has some patches for GRO and LVS.
Please send the results of "ethtool -k eth0" on all your nics / vlans ?
For TSO, I am not sure why and where it could matter...
next prev parent reply other threads:[~2010-12-03 11:29 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-03 10:34 TSO/GRO/LRO/somethingO breaks LVS on 2.6.36 Simon Kirby
2010-12-03 11:29 ` Eric Dumazet [this message]
2010-12-03 12:36 ` Simon Horman
2010-12-03 12:42 ` Simon Horman
2010-12-03 13:27 ` Ben Hutchings
2010-12-03 13:39 ` Simon Horman
2010-12-09 2:35 ` Simon Kirby
2010-12-09 2:51 ` Eric Dumazet
2010-12-22 23:39 ` Simon Kirby
2011-01-13 6:34 ` Simon Horman
2011-01-27 0:48 ` Simon Kirby
2011-01-27 1:36 ` Simon Horman
2011-01-27 7:42 ` Eric Dumazet
2011-01-27 14:42 ` Simon Horman
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