linux-kernel - Re: dvb usb issues since kernel 4.9

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Message-ID: <20180108231656.3bbd1968@redhat.com>
Date:   Mon, 8 Jan 2018 23:16:56 +0100
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Josef Griebichler <griebichler.josef@....at>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Rik van Riel <riel@...hat.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Hannes Frederic Sowa <hannes@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        LMML <linux-media@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        torvalds@...ux-foundation.org
Subject: Re: dvb usb issues since kernel 4.9

On Mon, 8 Jan 2018 22:44:27 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> On Mon, Jan 08, 2018 at 10:31:09PM +0100, Jesper Dangaard Brouer wrote:
> > I did expected the issue to get worse, when you load the Pi with
> > network traffic, as now the softirq time-budget have to be shared
> > between networking and USB/DVB. Thus, I guess you are running TCP and
> > USB/mpeg2ts on the same CPU (why when you have 4 CPUs?...)  
> 
> Isn't networking also over USB on the Pi ?

Darn, that is true. Looking at the dmesg output in http://ix.io/DOg:

[    0.405942] usbcore: registered new interface driver smsc95xx
[    5.821104] smsc95xx 1-1.1:1.0 eth0: link up, 100Mbps, full-duplex, lpa 0x45E1

I don't know enough about USB... is it possible to control which CPU
handles the individual USB ports, or on some other level (than ports)?

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer