Re: rt for newbie

[Carsten Emde <Carsten.Emde@osadl.org>]

Hi Dennis,

>>  [..]
>> 2. Configure the kernel for RT
>> # make menuconfig
>> Processor type and features --->
>> [ ] Tickless System (Dynamic Ticks)
>> Preemption Model (Fully Preemptible Kernel (RT)) --->
>> Kernel hacking --->
>> [ ] Check for stack overflows
> I think, your small "howto" is a little confusing. You are describing
> the kernel options needed for RT-capabilities, but there is no asterisk
> within the square brackets in order to show, that they should be
> enabled. The way it is written in your email, it seems like they should
> be disabled. Or did you really mean to disable the "Tickless System"
> option and the "Check for stack overflows" option?
Thank you for pointing this out. My description may, indeed, be 
misleading. I simply wanted to show how the line of the configuration 
menu should look like, i.e. not crossed -> not enabled.

Checking for stack overflows almost certainly leads to a longer 
worst-case latency and, while tickless operating is good for the 
financial budget, it may be bad for the real-time behavior. The latter 
applies to a configuration that allows the processor to enter a sleep 
state when idle and to a situation when rarely occurring external events 
trigger a real-time process so the processor has time to go to sleep.

Thanks,
	-Carsten.