Re: AW: [Xenomai-help] vxworks- and posix-skin simultaneously

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

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Roderik_Wildenburg@domain.hid wrote:
>>> Can anybody tell me about the actual state of using 
>> vxworks-skin and posix-skin simultaneously ? Is it possible, 
>> compiling one application with vxWorks-skin and an other one 
>> with the posix-skin and to use/execute these two applications 
>> simultaneously on one system ?
>>
>> Yes, feasible. There are example applications available for 
>> both skins, so setting up your own quick test will not take 
>> you much time.
>>
>>> In an earlier posting I have read, that all skins (or at 
>> least the native and the posix one) should be compiled as 
>> modules, so they do not overide the timer mode. Is this still 
>> true ? And if yes, dosn?t need the posix skin an aperiodic 
>> timer, but the timer is set to periodic mode by the vxworks 
>> skin ? So, can an vxworks application and an posix 
>> applications run together ??
>>
>> It's true that the vxworks skin still forces the nucleus into 
>> periodic timer mode. This is a known shortcoming of the 
>> current timer subsystem.
>> As announced earlier, we are aiming at a redesign to overcome 
>> this during the 2.4 development cycle. Ideas exist, remaining 
>> issues are also identified. But our resources are still 
>> limited, so there is no promise on a time-frame.
>>
> 
> 
>> Anyway, if you do not rely on having sub-tick timer precision 
>> for the posix applications you are planning, the available 
>> support should already be fine for you.
>>
> 
> Sorry, but what does "sub-tick timer precision" mean (isn?t the timer counting ticks) ?

I mean that you can only rely on tick resolution for both skins with the
currently available timer subsystem. In the future the vxworks skin tick
will be mapped on a periodic timer in an exclusively one-shot (high
resolution) timer implementation.

> Do I have to use the posix timers in a different way, when using periodic mode, or is just the timer resolution changing (incremnting by 1000000 when the period is  1ms e.g.) ?

The time unit of posix services remain nanoseconds, just the resolution
changes.

> What is a reasonable value for the timer period in the kenrel settings (1ms=1000000 ns ?)

Depends on available CPU resources on the target (check the load under
2.3-rc2 via /proc/xenomai/stat) and the required minimal resolution
(often defined by the fastest periodic job).

Jan


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