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Huge Pages on Mac OS X

The Mac OS X mmap man page says that you can select superpages, and I understand that this is the same as huge Linux pages.

https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man2/mmap.2.html

However, the following simple test fails on Mac OS X (Yosemite 10.10.5):

#include <stdio.h>
#include <sys/mman.h>
#include <mach/vm_statistics.h>

int
main()
{
    void *p = mmap((void *) 0x000200000000, 8 * 1024 * 1024,
                   PROT_READ | PROT_WRITE,
                   MAP_ANON | MAP_FIXED | MAP_PRIVATE,
                   VM_FLAGS_SUPERPAGE_SIZE_2MB, 0);
    printf("%p\n", p);
    if (p == MAP_FAILED)
        perror(NULL);
    return 0;
}

Output:

0xffffffffffffffff
Cannot allocate memory

The result is the same as MAP_FIXEDremoved from the flags and NULLspecified as an address argument. Replacing VM_FLAGS_SUPERPAGE_SIZE_2MBwith -1leads to the expected result, that is, an error does not occur, but, obviously, the allocated memory space uses regular 4k pages.

What could be a problem when distributing superpages this way?

+4
1

Mac OS 10.10.5:

#include <stdio.h>
#include <sys/mman.h>
#include <mach/vm_statistics.h>

int
main()
{
    void *p = mmap(NULL,
                   8*1024*1024,
                   PROT_READ | PROT_WRITE,
                   MAP_ANON | MAP_PRIVATE,
                   VM_FLAGS_SUPERPAGE_SIZE_2MB, // mach flags in fd argument
                   0);
    printf("%p\n", p);
    if (p == MAP_FAILED)
        perror(NULL);
    return 0;
}
-1

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