[Click] About queues scheduling

[Roberto Riggio]

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 <mailto: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
>     <mailto: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 421157
www.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.