Section: Linux Programmer's Manual (2)
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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
were introduced in Linux 2.5.36 and removed again in 2.5.54.
They existed only on i386 and ia64 (when built with
In Linux 2.4.20 the syscall numbers exist,
but the calls fail with the error
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
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.
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
and inherited by child processes.
tells which page is being freed: it was the return value of a
(The memory is first actually freed when all users have released it.)
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
argument is ignored, unless
In that case, if
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.
returns the allocated virtual address, and
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 file system can be used instead.
Memory backed by huge pages (if the CPU supports them) is obtained by
to map files in this virtual file system.
The maximal number of huge pages can be specified using the
This page is part of release 3.27 of the Linux
A description of the project,
and information about reporting bugs,
can be found at
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This document was created by
using the manual pages.