Thread (10 messages) 10 messages, 4 authors, 2011-10-31

Re: rt for newbie

From: Carsten Emde <hidden>
Date: 2011-10-28 17:02:08

Hi Dennis,
quoted
 [..]
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.
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