[Xenomai-help] heap allocation in xenomai

[Xenomai-help] heap allocation in xenomai

[manoj kumar]

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Hi,

Could anybody tell me about heap allocation in xenomai by API
rt_heap_create().

Why heap creation is required? Please tell the uses in detail?

Can kmalloc & free be used in any RT program at kernel space? If yes, Are
there any limitation on that? if Yes, then which are those.

Thanks & Regards
Manoj

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Re: [Xenomai-help] heap allocation in xenomai

[Jan Kiszka]

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manoj kumar wrote:
> Hi,
> 
> Could anybody tell me about heap allocation in xenomai by API
> rt_heap_create().
> 
> Why heap creation is required? Please tell the uses in detail?

The native skin's heaps provide means to reserve separate memory pools
and to perform deterministic allocation on it (as far as the heap usage
patterns are known).

For further derails, please read the API documentation and consult e.g.
the demo code: ksrc/skins/native/snippets/local_heap.c. Or ask a bit
more concrete questions.

> 
> Can kmalloc & free be used in any RT program at kernel space? If yes, Are
> there any limitation on that? if Yes, then which are those.

You can, but only during module init/cleanup, *NOT* while running inside
an RT task. That's because these Linux services may have been preempted
by Xenomai at any point while Linux was using it, and a re-entrance from
a Xenomai task would corrupt them.

Jan


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Re: [Xenomai-help] heap allocation in xenomai

[Jan Kiszka]

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[please keep the CC]

manoj kumar wrote:
> thanks jan
> 
> What is the limitation of size for heap creation? Is it 2Gb as given by
> XNHEAP_MAXEXTSZ (1 << 32)?b

Yes, given that you have enough (kernel) memory...

> 
> What is the limitation of size of data that can be read or write on the
> pipe?

Basically the same as above. Pipes are built on top of heaps.

Jan


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