Re: [Xenomai-help] Page faults

[Jan Kiszka <jan.kiszka@domain.hid>]

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Jeroen Van den Keybus wrote:
>> Maybe not all of your user memory is cleanly locked and got swapped out
>> (swapping activated?). If you don't see kernel oopses and your programs
>> don't receive segfaults, these faults are references to swapped out or
>> not yet mapped in pages. BTW, what does the kernel console tell you?
> 
> 
> I have a mlockall(MCL_CURRENT | MCL_FUTURE) in my main() (non-RT) task
> alright. Do I need to repeat that for the real-time tasks as well ?

You should not have to. I observed some cases where malloc'ed memory was
not immediately available, and you had to touch it first. I guess this
depends on how glibc requests the memory. So, if unsure, do an memset on
freshly allocated memory.

> 
> I'm quite certain that my kernel is configured for swapping. I did not see
> any harm in it, as a mlockall() was given. Should I try turning it off (if
> so, where) ?

Swapping does not do any harm, correct. I just wanted to check what may
trigger the problem.

> 
> I do not see 'oopses' and the dmesg log is clean, apart from one
> incidental spurious IRQ7 interrupt. Is 'dmesg' what you mean by 'kernel
> console' ?
> 

Ah, I oversaw some dependency. Try to enable CONFIG_XENO_OPT_DEBUG. Then
the nucleus should spit out which task is being relaxed due to faults:

"Switching XYZ to secondary mode after exception #? from user-space at
0x??? (pid ?)"

Jan



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