netdev - Re: bnx2 udp multicast packet loss and jtter

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Message-ID: <1308325964.3539.14.camel@edumazet-laptop>
Date:	Fri, 17 Jun 2011 17:52:44 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Kieran Kunhya <kierank@...encoder.com>
Cc:	netdev@...r.kernel.org
Subject: Re: bnx2 udp multicast packet loss and jtter

Le vendredi 17 juin 2011 à 16:35 +0100, Kieran Kunhya a écrit :
> On Fri, Jun 17, 2011 at 4:30 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> >
> > Le samedi 11 juin 2011 à 15:32 +0100, Kieran Kunhya a écrit :
> > > Hello,
> > >
> > > I get some bad packet loss and high jitter on a BCM5709. This is on
> > > kernel 2.6.38-8 - unfortunately using a newer kernel isn't an option
> > > right now.
> > > The bnx2 driver is version v2.0.23b.
> > >
> > > I've tried a lot of kenel types such as -lowlatency, -ck and vanilla.
> > > The thread doing the udp output is at realtime priority and the same
> > > thing happens with different applications.
> > >
> > > Example of jitter
> > > http://dl.dropbox.com/u/2701213/jitter.png
> > >
> > > Is there anything I can do to further diagnose this problem?
> > >
> >
> > Hi
> >
> > How is this jitter measured ?
> >
> > Is the link otherwise idle, or do you have a particular qdisc setup to
> > make sure packets from other flow wont have an effect ?
> 
> Thanks for the reply.
> The jitter is measured with an IPTV analyser. There are other devices
> on the same switch which don't have any jitter issues.
> The link is otherwise idle.

jitter has a precise meaning in RTP flows. Is this IPTV analyser using
this definition ?

Is this analyser running on the machine that sends frames, or another
machine ?

Are you sure the realtime thread fullfill its requirements ?
(RT priority wont help if this thread is cpu bounded)



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