[ECOS] Suitability of eCos

Pamulapati, Indrasena (CTS) pindrase@chn.cognizant.com
Tue Jan 16 11:08:00 GMT 2001


Hi Jesper,

Yes, the tick duaration controls the kernel scheduler and I dont need
scheduling at that rate.
But does'nt the tick duration also determine the smallest addressable time
unit.
What i mean is:

Let us consider the duration of a tick to be a reasonable value of
10millisec.
Now, if I want to send some data at, say 20ms from the start of a reference
point,
I will give a delay of 2ticks from the reference point and as u mentioned
send an interrupt to the driver after 2ticks.

Now, what if I want to send the data after 1 ms from the reference point. I
will not be able to specify the number of ticks I have to wait if tick
duration is 10ms. So what I thought was, I can decrease the tick duration to
less that 1ms, say 0.5ms and give a delay of 2ticks and then send the
interrupt. But this I guess will adversly affect the performance of the
system.

Jesper, actually I am quite a newbie wrt drivers and rtos's.
	Can you elaborate on
	 "Drivers doing IO should be driven separately, relying on device
interrupts, not scheduler interrupts, for state transitions." based on the
problem I mentioned above. I guess this may solve my problem.
 
Regards,
Indrasena

  

> -----Original Message-----
> From:	Jesper Skov [SMTP:jskov@redhat.com]
> Sent:	Tuesday, January 16, 2001 4:14 PM
> To:	Pamulapati, Indrasena (CTS)
> Cc:	ecos-discuss@sources.redhat.com
> Subject:	Re: [ECOS] Suitability of eCos
> 
> >>>>> "Pamulapati," == Pamulapati, Indrasena (CTS)
> <pindrase@chn.cognizant.com> writes:
> 
> Pamulapati,> the overhead involved in processing the tick.  But my
> Pamulapati,> application requires tick duration as low as a
> Pamulapati,> 100microseconds. I need to address such low time
> Pamulapati,> resolutions.
> 
> As Ramana pointed out, the tick duration controls little more than
> the kernel scheduler in eCos. Surely you don't need thread scheduling
> at that rate!?!
> 
> Drivers doing IO should be driven separately, relying on device
> interrupts, not scheduler interrupts, for state transitions.
> 
> But without further information about your application my comments
> above are just guesses and may not actually apply...
> 
> Jesper

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