netdev - Re: [RFC PATCH 0/2] net:setup XPS mapping for each online CPU

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Date:   Thu, 15 Mar 2018 18:20:31 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        intel-wired-lan@...ts.osuosl.org,
        Alexander Duyck <alexander.h.duyck@...el.com>
Subject: Re: [RFC PATCH 0/2] net:setup XPS mapping for each online CPU

Hi,

On Thu, 2018-03-15 at 15:59 +0000, Eric Dumazet wrote:
> On Thu, Mar 15, 2018 at 8:51 AM Paolo Abeni <pabeni@...hat.com> wrote:
> > I'm sorry, I do not follow. AFAICS with unconnected sockets without XPS
> > we always hit the netdev_pick_tx()/skb_tx_hash()/skb_flow_dissect()
> > overhead in xmit path.
> 
> Then fix this if you want, instead of fixing one NIC only, or by enforcing
> XPS by all NIC.
> 
> For unconnected sockets, picking the TX queue based on current cpu is good,
> we do not have to enforce ordering as much as possible.
> 
> (pfifo_fast no longer can enforce it anyway)

Thank you for the prompt reply. 

I'm double checking to avoid misinterpretation on my side: are you
suggesting to plug a CPU-based selection logic for unconnected sockets
in netdev_pick_tx() or to cook patches like 2/2 for all the relevant
NICs? 

Thanks!

Paolo