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

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Date:	Sun, 30 Dec 2012 00:08:48 +0400
From:	Andrew Vagin <avagin@...allels.com>
To:	Eric Dumazet <eric.dumazet@...il.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, Dec 29, 2012 at 11:41:02AM -0800, Eric Dumazet wrote:
> 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

I don't have access to the host. I'm going to test your patch tomorrow.
Thanks.

> 
> And of course, you should make sure all your bnx2 interrupts are handled
> by the same cpu.
All bnx interrupts are handled on all cpus. They are handled on the same
cpu, if a kernel is booted with msi_disable=1.

Is it right, that a received window will be less, if packets are not sorted?
Looks like a bug.

I want to say, that probably it works correctly, if packets are sorted.
But I think if packets are not sorted, it should work with the same
speed, cpu load and memory consumption may be a bit more.

> 
> 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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