[Click] About queues scheduling

[Cliff Frey]

Oh yes, sorry for misunderstanding.

We actually had issues with KernelTun.  We ended up adding a BURST parameter
to it.  There are weird interactions between selected() and tasks where
selected() does not get called as often as one might hope.  You could also
try changing the _tasks_per_iter to be much much lower (like 2) and see if
it helps...

I can look into giving you an updated KernelTun with a BURST param if you
are interested, but it might take me a few days to get to it.

Cliff

On Wed, Apr 20, 2011 at 9:50 AM, Roberto Riggio <
roberto.riggio at create-net.org> wrote:

>  Packets are not coming from a fromdevice element, but rather are injected
> from a
> kerneltun element. Traffic is generated in user space by iperf.
>
> The generation rate is 10 mbps so it cannot be transmitted over the
> wireless
> link that is running at the static rate of 6 mbps. However, the packets are
> not
> lost on the link, but somewhere between kerneltun and iperf.
>
> R.
>
> Il 20/04/2011 18:17, Cliff Frey ha scritto:
>
> 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 <http://www.create-net.org/%7Erriggio>
>> --------------------------------------------------------
>>
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>
>
>
> --
> --------------------------------------------------------
> 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 421157www.create-net.org/~rriggio
> --------------------------------------------------------
>
> The information transmitted is intended only for the person or entity to
> which it is addressed and may contain confidential and/or privileged
> material. Any review, retransmission, dissemination or other use of, or
> taking of any action in reliance upon, this information by persons or
> entities other than the intended recipient is prohibited according to
> the Italian Law 196/2003 of the Legislature. If you received this in
> error, please contact the sender and delete the material from any
> computer.
>
> Le informazioni contenute in questo messaggio di posta elettronica e nei
> file allegati sono da considerarsi strettamente riservate. Il loro
> utilizzo e' consentito esclusivamente al destinatario del messaggio, per
> le finalita' indicate nel messaggio stesso. Qualora riceveste questo
> messaggio senza esserne il destinatario, Vi preghiamo cortesemente di
> darcene notizia via e-mail e di procedere alla cancellazione del
> messaggio stesso dal Vostro sistema. Trattenere il messaggio stesso,
> divulgarlo anche in parte, distribuirlo ad altri soggetti, copiarlo,
> od utilizzarlo per finalita' diverse, costituisce comportamento
> contrario ai principi dettati dal D. Lgs. 196/2003.
>
>