---
name: "get_hugepage_region"
section: "3"
platform: "linux"
package: "libhugetlbfs-dev"
version: "2.24-1+b1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/get_hugepage_region"
---

# get\_hugepage\_region(3)

Allocate and free regions of memory that use hugepages where possible

## 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);**

## DESCRIPTION

**get\_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 allocating a region of memory. The current default is:\
   	GHR\_FALLBACK \| 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 ALSO

*[oprofile(1)](/oprofile/1.md)* , *[gethugepagesize(3)](/gethugepagesize/3.md)* , *[get\_huge\_pages(3)](/get_huge_pages/3.md)* , *[libhugetlbfs(7)](/libhugetlbfs/7.md)*

## AUTHORS

libhugetlbfs was written by various people on the libhugetlbfs-devel mailing list.