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, specify this flag.
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.
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.