выделить или освободить огромные страницы (allocate or free huge pages)
Имя (Name)
alloc_hugepages, free_hugepages - allocate or free huge pages
Синопсис (Synopsis)
void *syscall(SYS_alloc_hugepages, int key, void *addr, size_t len,
int prot, int flag);
int syscall(SYS_free_hugepages, void *addr);
Note: glibc provides no wrappers for these system calls,
necessitating the use of syscall(2).
Описание (Description)
The system calls alloc_hugepages() and free_hugepages() were
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 swapped.
The key 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.
The addr argument of free_hugepages() tells which page is being
freed: it was the return value of a call to alloc_hugepages().
(The memory is first actually freed when all users have released
it.) The addr argument of alloc_hugepages() is a hint, that the
kernel may or may not follow. Addresses must be properly
aligned.
The len argument is the length of the required segment. It must
be a multiple of the huge page size.
The prot argument specifies the memory protection of the segment.
It is one of PROT_READ, PROT_WRITE, PROT_EXEC.
The flag argument is ignored, unless key is positive. In that
case, if flag is IPC_CREAT, then a new huge page segment is
created when none with the given key existed. If this flag is
not set, then ENOENT is returned when no segment with the given
key exists.
Возвращаемое значение (Return value)
On success, alloc_hugepages() returns the allocated virtual
address, and free_hugepages() returns zero. On error, -1 is
returned, and errno is set to indicate the error.
Ошибки (Error)
ENOSYS The system call is not supported on this kernel.
Файлы (Files)
/proc/sys/vm/nr_hugepages
Number of configured hugetlb pages. This can be read and
written.
/proc/meminfo
Gives info on the number of configured hugetlb pages and
on their size in the three variables HugePages_Total,
HugePages_Free, Hugepagesize.
Стандарты (Conforming to)
These extinct system calls were specific to Linux on Intel
processors.
Примечание (Note)
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(2) to map files in this virtual
filesystem.
The maximal number of huge pages can be specified using the
hugepages= boot parameter.
