Hi,
With Xenomai Mercury (specifically the PSOS skin, but that doesn't
matter for this question), the minimal stack size applied is
PTHREAD_STACK_MIN * 4, even if the caller requested a smaller one.
On MIPS, and some other architectures, PTHREAD_STACK_MIN is already 128K:
(<glibc>/ports/sysdeps/unix/sysv/linux/mips/nptl/bits/local_lim.h)
/* Minimum size for a thread. At least two pages with 64k pages. */
#define PTHREAD_STACK_MIN 131072
With Xenomai multiplying this with 4, every thread has half a megabyte
of stack, which is way too much for systems with a large number of
threads.
It is possible to limit this in other ways, by setting 'ulimit -s 128'
for example, but it is a dirty workaround in my opinion.
What is the real minimum stack requirement for Xenomai? I cannot
imagine that this is in the order of 512K.
With PTHREAD_STACK_MIN varying so much on different platforms, what
about code like:
minimum_stacksize = MAX(XENOMAI_STACK_MIN, PTHREAD_STACK_MIN);
if (stacksize < minimum_stacksize) {
stacksize = minimum_stacksize;
}
where XENOMAI_STACK_MIN is a value that is not calculated based on
PTHREAD_STACK_MIN?
With this approach, systems with 16K PTHREAD_STACK_MIN could still get
64K minimum stack in case the xenomai minimum stack size is 64K, while
not negatively impacting systems that have 128K PTHREAD_STACK_MIN.
(Note that for systems with 4K/8K pages, the PTHREAD_STACK_MIN of 128K
(two 'pages' taken for 64K) is already very exaggerated)
Thanks,
Thomas
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