[Click] question on element scheduling

[Indian Mogul]

Thanks Nikitas & Beyers. In brief, it means I'll have
to play with the click scheduler. In the meantime let
me read the section on TASKS and TIMERS; before I
shoot in further questions.

Cheers!!
IM

--- Nikitas Liogkas <nikitas at CS.UCLA.EDU> wrote:
> What Beyers is saying is correct, just bear in mind
> that timers have 
> coarse granularity; they get processed every 32
> (default) scheduling 
> epochs. So, for example, if you want your code to
> run at time t, you 
> should schedule the timer for time t-dt, in order to
> maximize the 
> probability that it WILL actually run at time t. If
> this is confusing, 
> let me know and I can elaborate more.
> 
> Hope this helps!
> 
> nikitas
> 
> Beyers Cronje wrote:
> > Hi IM,
> > 
> > See comments below. 
> > 
> > Beyers
> > 
> > On 5/20/05, Indian Mogul <indian_mogul at yahoo.com>
> wrote:
> > 
> >>Hi,
> >>   I have a simple question for which I have been
> >>laboring for quite some time.
> >>In my router config file, I want one of my click
> >>element to periodically check for the value of TTL
> in
> >>the table irrespective of whether packets are
> recvd or
> >>not? The name of the element is check_ttl() and
> the
> >>path where it is introduced is:
> >>//Fromdevice()->classifier->get_flow_id()
> >>  ->check_ttl()->//
> >>
> >>so, inside the element I have code that does:
> >>// Check current time.
> >>// If (current_time > expiry time)
> >>//    flush_the _entry
> >>//   else
> >>//     do nothing.
> >>
> >>1. Now, my question is, will the element
> "check_ttl()"
> >>get automatically scheduled at the right time
> >>irrespective of whether packets are there or not?
> > 
> > 
> > The short answer is no. 
> > 
> > My understading is only schedulable tasks and
> timers are processed by
> > the scheduler. All schedulable elements such as
> PollDevice/FromDevice
> > implements a task, the scheduler calls the
> element's run_task method
> > when scheduled. Unschedulable elements are called
> implicitly through
> > the push/pull interfaces from the schedulable
> element.
> > 
> > For your requirements a timer might be the way to
> go, maybe inside an
> > information element, which does not sit in packet
> flow path, in other
> > words it does not implement and push/pull
> interfaces. Look at the
> > existing elements on implementing timers.
> > 
> > Have another look in the programming manual for
> TASKS and TIMERS.
> > 
> > For your scenarion an informational element  
> > 
> > 
> >>2. Since click is single threaded, how do I
> schedule
> >>the check_ttl() if ans to (1) is false?
> > 
> > 
> > See above.
> > 
> > 
> >>Thanks?
> >>IM
> >>
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