Fw: Re: Pb with FPUsupport and VMalloc activated on PPC platform

Paolo Mantegazza mantegazza at aero.polimi.it
Wed Oct 27 17:41:37 CEST 2004

Wolfgang Grandegger wrote:
> I wonder that you can enable RTAI_CONFIG_MALLOC_VMALLO. In previous
> versions of RTAI it was disabled, at least.
It is. If you enable the extended configuration option then under the 
RTAI proper menu you can config vmalloc and the size of the global heap. 
It should be noticed that it is better to download the latest malloc.c 
in the CVS if one wants to exceed 128 using kmalloc.

What is important is that the RTAI malloc area is now usable from user 
space also, by calling rt_global_heap_open. Moreover blocks allocated on 
it can be shared between kernel and user space without allocating a 
specif shared memory area. Requires using the shared memory module anyhow.
Such a feature is available only using vmalloc, sharing kmalloced blocks 
requires to write too much mapping to me :-).

The fact that vmalloc does not work on the PPC could be worth to be 
understood. So with the latest malloc.c there is no need to use vmalloc 
if one works in kernel space only.


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