alloc_hugepages, free_hugepages - allocate or free huge pages
void *alloc_hugepages(int key, void *addr, size_t len,
int prot, int flag);
int free_hugepages(void *addr);
The system calls alloc_hugepages
() and free_hugepages
introduced in Linux 2.5.36 and removed again in 2.5.54. They existed only on
i386 and ia64 (when built with CONFIG_HUGETLB_PAGE
). In Linux 2.4.20,
the syscall numbers exist, but the calls fail with the error ENOSYS
On i386 the memory management hardware knows about ordinary pages (4 KiB)
and huge pages (2 or 4 MiB). Similarly ia64 knows about huge pages of
several sizes. These system calls serve to map huge pages into the process's
memory or to free them again. Huge pages are locked into memory, and are not
argument is an identifier. When zero the pages are private, and
not inherited by children. When positive the pages are shared with other
applications using the same key
, and inherited by child processes.
argument of free_hugepages
() tells which page is being
freed: it was the return value of a call to alloc_hugepages
memory is first actually freed when all users have released it.) The
argument of alloc_hugepages
() is a hint, that the kernel
may or may not follow. Addresses must be properly aligned.
argument is the length of the required segment. It must be a
multiple of the huge page size.
argument specifies the memory protection of the segment. It is
one of PROT_READ
argument is ignored, unless key
is positive. In that
case, if flag
, then a new huge page segment is
created when none with the given key existed. If this flag is not set, then
is returned when no segment with the given key exists.
On success, alloc_hugepages
() returns the allocated virtual address, and
() returns zero. On error, -1 is returned, and
is set appropriately.
- The system call is not supported on this kernel.
- Number of configured hugetlb pages. This can be read and written.
- Gives info on the number of configured hugetlb pages and on their size in
the three variables HugePages_Total, HugePages_Free, Hugepagesize.
These calls are specific to Linux on Intel processors, and should not be used in
programs intended to be portable.
These system calls are gone; they existed only in Linux 2.5.36 through to
2.5.54. Now the hugetlbfs filesystem can be used instead. Memory backed by
huge pages (if the CPU supports them) is obtained by using mmap
map files in this virtual filesystem.
The maximal number of huge pages can be specified using the hugepages=