netdev - Re: [BUG?] ixgbe: only num_online_cpus() of the tx queues are enabled

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Date:	Sun, 9 Mar 2014 01:43:32 -0500
From:	Ming Chen <v.mingchen@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	John Fastabend <john.r.fastabend@...el.com>
Cc:	netdev@...r.kernel.org, Erez Zadok <ezk@....cs.sunysb.edu>,
	Dean Hildebrand <dhildeb@...ibm.com>,
	Geoff Kuenning <geoff@...hmc.edu>
Subject: Re: [BUG?] ixgbe: only num_online_cpus() of the tx queues are enabled

On Sat, Mar 8, 2014 at 10:29 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> You do not need multiqueue to send traffic for few TCP flows, because
> packets will reach 64KB size very fast.

I am trying to experiment using only one queue for all the TCP flows.
But, how do we force that. I was thinking about XPS. But I just
realized that /sys/class/net/p3p1/queues/tx-n/xps_cpus only set which
CPUs can use them. How to let all CPUs choose one single tx queue? Or,
should I use mqprio and assign all flows to one tc that contains only
one tx queue?

>
> If you want fairness, then multiqueue wont do it, unless you add some
> kind of shaper.
>
> TCP is handling one flow, not an arbitrary number of flows.
>
> If you need fairness, then you need an AQM like FQ.
>

Yeah. You are right. However, if we really want fairness while using
mq, then should AQM and FQ be aware of mq or even the scheduling of
the queues?

Best,
Ming
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