[EMAIL PROTECTED] wrote:
memset should work with Xenomai heaps, I suspect your problem
is rather that the memory is not really allocated until you
memset it, which fails when no memory is available. In this
case, calling memset on memory allocated with malloc should
segfault the same way when the system memory is exhausted.
IIRC, this behaviour is documented in mlockall manual page.
Mr. Denk told me about this strange (for RTOSs) behaviour of the
Linux kernel. Therefore I used the Xenomai heap mechanism, expecting
allocated memory is allocated at once not some time later
(why do I allocate memory otherwise : to be shure memory is available).
Does Xenomai use the Linux allocation mechanism ??
Be careful with sysconf(_SC_AVPHYS_PAGES), it may include the
swap size, but when mlocking memory, your application can not
use swap pages, so, you should substract the size of swap, if any.
Also, what is the value of /proc/sys/vm/overcommit_memory on
your system ?
Our System does not have a swap device\space.
/proc/sys/vm/overcommit_memory = 0
(whatever this means)
I gave your program a try on my MPC5200 and got the following output
(after some corrections):
bash-2.05b# ./heap2
Start Heap
root_thread_init :
timer startedt
display task created
root_thread_init beendet
Available Memory 56238080 (Pagesize 4096)
heap 0 of size 16000000 created
Heap 0 allocated size 16000000
heap 1 of size 16000000 created
Heap 1 allocated size 16000000
heap 2 of size 16000000 created
Heap 2 allocated size 16000000
__alloc_pages: 0-order allocation failed (gfp=0x1f2/0)
Available Memory after allocation 8933376
__alloc_pages: 0-order allocation failed (gfp=0x1f0/0)
Heap 3 created with size 4218880
Heap 3 allocated size 4218880
Memory allocated in total : 52218880
Segmentation fault
The are some long delays (approx. 40 secs) around __alloc_pages. Finally
it crashes in memset. With the attached xenomai patch, which touches the
reserved page once, memset works fine. Let's wait what Philippe says. I
remember that the "touch" was needed for RTAI shared memory as well.
Wolfgang.
+ diff -u xenomai/ksrc/nucleus/heap.c.OLD xenomai/ksrc/nucleus/heap.c
--- xenomai/ksrc/nucleus/heap.c.OLD 2006-06-30 10:29:34.000000000 +0200
+++ xenomai/ksrc/nucleus/heap.c 2006-07-11 09:46:30.000000000 +0200
@@ -1044,8 +1044,10 @@
vabase = (unsigned long)ptr;
- for (vaddr = vabase; vaddr < vabase + size; vaddr += PAGE_SIZE)
+ for (vaddr = vabase; vaddr < vabase + size; vaddr += PAGE_SIZE) {
SetPageReserved(virt_to_page(__va_to_kva(vaddr)));
+ *(int *)vaddr = 0; /* touch page once */
+ }
} else {
/*
* Otherwise, we have been asked for some kmalloc()
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