netdev - Aw: Re: dvb usb issues since kernel 4.9

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Date:   Tue, 9 Jan 2018 17:51:09 +0100
From:   "Josef Griebichler" <griebichler.josef@....at>
To:     "Jesper Dangaard Brouer" <jbrouer@...hat.com>
Cc:     "Peter Zijlstra" <peterz@...radead.org>,
        "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: Aw: Re: dvb usb issues since kernel 4.9

Hi Linus,

your patch works very good for me and others (please see https://forum.libreelec.tv/thread/4235-dvb-issue-since-le-switched-to-kernel-4-9-x/?postID=77006#post77006). No errors in recordings any more.
The patch was also tested on x86_64 (Revo 3700) with positive effect.
I agree with the forum poster, that there's still an issue when recording and watching livetv at same time. I also get audio dropouts and audio is out of sync.
According to user smp kernel 4.9.73 with your patch on rpi and according to user jahutchi kernel 4.11.12 on x86_64 have no such issues.
I don't know if this dropouts are related to this topic.

If of any help I could provide perf output on raspberry with libreelec and tvheadend.

Regards,
Josef 

Gesendet: Montag, 08. Januar 2018 um 23:16 Uhr
Von: "Jesper Dangaard Brouer" <jbrouer@...hat.com>
An: "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
Betreff: 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[http://www.linkedin.com/in/brouer]