[Click] About queues scheduling

[Cliff Frey]

On Fri, Apr 22, 2011 at 12:59 AM, Roberto Riggio <
roberto.riggio at create-net.org> wrote:

> Il 22/04/2011 09:31, Cliff Frey ha scritto:
>
>  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...
>>
>
> what is the meaning of the _tasks_per_iter variable? Which are the
> sideeffects of lowering it? Does it means that tasks (and timers???) will be
> checked fewer times
> per iteration allowing click to schedule also (for example) the kerneltun
> element?


I'm not positive off the top of my head, would need to look at the source,
but essentially yes, I think it is the number of task runs between checking
timers/select().


> 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.
>>
> Shall the BURST param allow to iterate N times over this
>
>    int cc = read(_fd, p->data(), _mtu_in);
>
> and the following if block in KernelTun::selected?
>

Give or take, yes.  It also needs to create a new packet each time.  You
also need to ignore EAGAIN (well, break out of the loop, but don't print
anything or treat it as an error).

Cliff