[Click] About queues scheduling

[Cliff Frey]

I would expect that you are _not_ CPU limited.  This is what I would expect
to see if FromDevice is just only rarely scheduled.

If you are still worried about fairness, you can set the BURST parameter on
FromDevice to be higher, but I really think that the issue is that
FromDevice's task is not active, because the device has not received any
more packets.

You can also check FromDevice's "drops" handler to make sure that FromDevice
is not being starved.

Cliff

On Wed, Apr 20, 2011 at 1:55 AM, Roberto Riggio <
roberto.riggio at create-net.org> wrote:

> Hi,
>
> I have some doubts about how push and pull are scheduled.
>
> I'm running click on two wireless routers and I'm generating some
> traffic between them using iPerf. Wireless interfaces are operating in
> monitor mode and click is running in userspace.
>
> The configuration essentially consist of:
>
> KernelTun
>  -> CheckIPHeader
>  -> ... other push elements that set route etc. ...
>  -> FullNoteQueue
>  -> WifiEncap, SetTXRate, Radiotapencap
>  -> ToDevice
>
> The tx rate is statically set to 6 mbps. The strange this is that if
> I generate traffic with Iperf at a very high rate (e.g. 10Mbps) I
> do get an high packet loss as expected, but there is only one packet
> in the queue.
>
> I've added some debug message to the Queue' push and pull method
> and this is what I get:
>
> push
> pull
> pull
> pull
> pull
> pull
> pull
> pull
> pull
> pull
> pull
> pull
> push
> pull
> pull
> pull
> pull
> pull
> pull
> pull
> pull
> pull
> pull
> pull
> push
>
> basically it seems that the driver is alway trying to pull from the
> queue, until the
> _empty_note is put to sleep and only then a packet is pushed into the
> queue.
>
> What I would expect is that incoming packet should be pushed in to the
> queue
> and then eventually dropped if todevice cannot pull them all. Am I
> missing somthing?
>
> R.
>
> --
> --------------------------------------------------------
> Roberto Riggio, Ph.D.
> CREATE-NET
> Network&  Security Solutions for Pervasive Computing Systems (iNSPIRE)
> Senior Researcher
> Via alla Cascata 56/D - 38123 Povo Trento (Italy)
> e-mail: roberto.riggio at create-net.org
> Tel: (+39) 0461 408400 - interno/extension 708
> Fax: (+39) 0461 421157
> www.create-net.org/~rriggio
> --------------------------------------------------------
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