CentOS 7.0 - man page for free_hugepage_region (centos section 3)
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get_hugepage_region, free_hugepage_region - Allocate and free regions of memory that use
hugepages where possible
void *get_hugepage_region(size_t len, ghr_t flags);
void free_hugepage_region(void *ptr);
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.
Use base pages if there are an insufficient number of huge pages.
Use hugepages or return NULL.
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, spec-
ify this flag.
The library chooses a sensible combination of flags for allocating a region of mem-
ory. 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.
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.
oprofile(1) , gethugepagesize(3) , get_huge_pages(3) , libhugetlbfs(7)
libhugetlbfs was written by various people on the libhugetlbfs-devel mailing list.
November 7, 2008 GET_HUGEPAGE_REGION(3)
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