From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <netdev-owner@vger.kernel.org>
Received: from mx3-rdu2.redhat.com ([66.187.233.73]:55858 "EHLO mx1.redhat.com"
        rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP
        id S1751466AbeCORUd (ORCPT <rfc822;netdev@vger.kernel.org>);
        Thu, 15 Mar 2018 13:20:33 -0400
Message-ID: <1521134431.2681.26.camel@redhat.com>
Subject: Re: [RFC PATCH 0/2] net:setup XPS mapping for each online CPU
From: Paolo Abeni <pabeni@redhat.com>
To: Eric Dumazet <edumazet@google.com>
Cc: netdev <netdev@vger.kernel.org>,
        David Miller <davem@davemloft.net>,
        Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
        intel-wired-lan@lists.osuosl.org,
        Alexander Duyck <alexander.h.duyck@intel.com>
Date: Thu, 15 Mar 2018 18:20:31 +0100
In-Reply-To: <CANn89iLJOVuN-1j+9_qr_LaU7AE6COHdnp4Rc7fe9p6_s=hCCA@mail.gmail.com>
References: <cover.1521124830.git.pabeni@redhat.com>
         <CANn89iKcHzs2enS-CjNx3xJWwXwjX9Uu_7JYihOR4=HPsQLj6Q@mail.gmail.com>
         <1521129082.2681.13.camel@redhat.com>
         <CANn89iLJOVuN-1j+9_qr_LaU7AE6COHdnp4Rc7fe9p6_s=hCCA@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

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@redhat.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