netdev - Re: Slow speed of tcp connections in a network namespace

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Date:	Sat, 29 Dec 2012 11:41:02 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andrew Vagin <avagin@...allels.com>
Cc:	netdev@...r.kernel.org, vvs@...allels.com,
	Michał Mirosław <mirq-linux@...e.qmqm.pl>
Subject: Re: Slow speed of tcp connections in a network namespace

On Sat, 2012-12-29 at 19:58 +0100, Eric Dumazet wrote:
> Le samedi 29 décembre 2012 à 09:40 -0800, Eric Dumazet a écrit :
> 
> > 
> > Please post your new tcpdump then ;)
> > 
> > also post "netstat -s" from root and test ns after your wgets
> 
> Also try following bnx2 patch.
> 
> It should help GRO / TCP coalesce
> 
> bnx2 should be the last driver not using skb head_frag

And of course, you should make sure all your bnx2 interrupts are handled
by the same cpu.

Or else, packets might be reordered because the way dev_forward_skb()
works.

(CPU X gets a bunch of packets from eth0, forward them via netif_rx() in
the local CPU X queue, NAPI is ended on eth0)

CPU Y gets a bunch of packets from eth0, forward them via netif_rx() in
the local CPU Y queue.

CPU X and Y process their local queue in // -> packets are delivered Out
of order to TCP stack

Alternative is to setup RPS on your veth1 device, to force packets being
delivered/handled by a given cpu





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