free_hugepages


SYNOPSIS
       void *alloc_hugepages(int key, void *addr, size_t len,
                             int prot, int flag);

       int free_hugepages(void *addr);

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  pro-
       cesses.

       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 argu-
       ment 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.

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 appropriately.

ERRORS
       ENOSYS The system call is not supported on this kernel.

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

       The  maximal number of huge pages can be specified using the hugepages=
       boot parameter.


COLOPHON
       This page is part of release 3.35 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://man7.org/linux/man-pages/.



Linux                             2007-05-31                ALLOC_HUGEPAGES(2)
Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2017 Hurricane Electric. All Rights Reserved.