alloc_hugepages, free_hugepages — allocate or free huge pages
The system calls
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
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.
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
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
is the length of the required segment. It must be a multiple
of the huge page size.
specifies the memory protection of the segment. It is one of
is ignored, unless
key is positive. In that case,
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.
alloc_hugepages() returns the allocated
virtual address, and
free_hugepages() returns zero. On error,
−1 is returned, and
is set appropriately.
Number of configured hugetlb pages. This can be read and
/proc/meminfo Gives info on
the number of configured hugetlb pages and on their size in
the three variables HugePages_Total, HugePages_Free,
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(2) to map files in this virtual filesystem.
The maximal number of huge pages can be specified using
This page is part of release 4.07 of the Linux
man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
Copyright 2003 Andries E. Brouwer (aebcwi.nl)
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