[Xenomai-help] do memory functions switch to secondary mode ?

[Xenomai-help] do memory functions switch to secondary mode ?

[Roderik_Wildenburg]

Does any of the memory functions like :
memcopy,
memset,
bzero,

:
:

cause Xenomai to switch to secondary mode ?
I am asking as I have a high priority task, which mesures its
periodicity (set to 1ms).
This task is using just rt_-functions and memcpy.
When in low priority tasks memory intensively is used (memset,
rt_heap_alloc, rt_heap_create, NFS-transfers in Linux threads), the
cycle time of the high priority task inreases to nearly twice the time
it has been set up (2ms++; at least 1 time, as I just measure maxima).

Is this possible, or am I doing something wrong ?

Tanks a lot
Roderik

Re: [Xenomai-help] do memory functions switch to secondary mode ?

[Jan Kiszka]

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Roderik_Wildenburg@domain.hid wrote:
> Does any of the memory functions like :
> memcopy,
> memset,
> bzero,
> 
> :
> :
> 
> cause Xenomai to switch to secondary mode ?
> I am asking as I have a high priority task, which mesures its
> periodicity (set to 1ms).
> This task is using just rt_-functions and memcpy.
> When in low priority tasks memory intensively is used (memset,
> rt_heap_alloc, rt_heap_create, NFS-transfers in Linux threads), the
> cycle time of the high priority task inreases to nearly twice the time
> it has been set up (2ms++; at least 1 time, as I just measure maxima).
> 
> Is this possible, or am I doing something wrong ?

Try catching unwanted context switches via the SIGXCPU signal. Given you
have a sane glibc, non of those functions should cause a context switch
- unless you touch some piece of memory for the first time (lazy
mapping...).

[Unfortunately, the I-pipe tracer is only available over 2.6 so far.
Otherwise, putting a xntrace_user_freeze() right at that line in your
application where you detect the deadline miss would give a nice view
back in history.]

Jan


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Re: [Xenomai-help] do memory functions switch to secondary mode ?

[Philippe Gerum]

On Tue, 2006-07-11 at 14:27 +0200, Roderik_Wildenburg@domain.hid wrote:
> Does any of the memory functions like :
> memcopy,
> memset,
> bzero,
> 
> :
> :
> 
> cause Xenomai to switch to secondary mode ?

No, unless a page fault is raised as a result of treading on the target
memory.

> I am asking as I have a high priority task, which mesures its
> periodicity (set to 1ms).
> This task is using just rt_-functions and memcpy.
> When in low priority tasks memory intensively is used (memset,
> rt_heap_alloc, rt_heap_create, NFS-transfers in Linux threads), the
> cycle time of the high priority task inreases to nearly twice the time
> it has been set up (2ms++; at least 1 time, as I just measure maxima).
> 
> Is this possible, or am I doing something wrong ?
> 

Do you observe this weird behaviour at the same time the kernel emits
allocation failure messages?

> Tanks a lot
> Roderik
> 
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> Xenomai-help mailing list
> Xenomai-help@domain.hid
> https://mail.gna.org/listinfo/xenomai-help
-- 
Philippe.