GET_HUGEPAGE_REGION(3)GET_HUGEPAGE_REGION(3)NAME
get_hugepage_region, free_hugepage_region - Allocate and free regions
of memory that use hugepages where possible
SYNOPSIS
#include <hugetlbfs.h>
void *get_hugepage_region(size_t len, ghr_t flags);
void free_hugepage_region(void *ptr);
DESCRIPTIONget_hugepage_region() allocates a memory region len bytes in size
backed by hugepages. Hugepages may be of benefit to applications that
use large amounts of address space and suffer a performance hit due to
TLB misses. Wall-clock time or oprofile can be used to determine if
there is a performance benefit from using hugepages or not.
Unlike get_huge_pages(), len does not have to be hugepage-aligned
although memory may be wasted due to alignment. The caller may also
specify that base pages be used in the event there are no hugepages
available.
The flags argument changes the behaviour of the function. Flags may be
or'd together.
GHR_FALLBACK
Use base pages if there are an insufficient number of huge
pages.
GHR_STRICT
Use hugepages or return NULL.
GHR_COLOR
When specified, bytes that would be wasted due to alignment are
used to color the buffer by offsetting it by a random cacheline
within the hugepage. This avoids a performance problem whereby
multiple buffers use the same cache lines at the same offsets.
If it is not important that the start of the buffer be page-
aligned, specify this flag.
GHR_DEFAULT
The library chooses a sensible combination of flags for allocat‐
ing a region of memory. The current default is: GHR_FALL‐
BACK | GHR_COLOR
free_hugepage_region() frees a region of memory allocated by
get_hugepage_region(). The behaviour of the function if another pointer
is used, valid or otherwise, is undefined.
RETURN VALUE
On success, a pointer is returned for to the allocated memory. On
error, NULL is returned. errno will be set based on what the failure of
mmap() was due to.
SEE ALSOoprofile(1) , gethugepagesize(3) , get_huge_pages(3) , libhugetlbfs(7)AUTHORS
libhugetlbfs was written by various people on the libhugetlbfs-devel
mailing list.
November 7, 2008 GET_HUGEPAGE_REGION(3)