09-18-2014
Quote:
Originally Posted by
achenle
In your case, I suspect the C++ core is probably mmap() anonymous memory, requesting large pages, and using them for video processing buffers. And, unfortunately, then releasing them, allowing the page cache to fragment the large pages. Eventually you get to the point where there are no large pages available because of fragmentation.
Would turning off hugepages somehow be a solution? It could be just one bit in a binary's code segment somewhere... There'd be a performance hit from using small pages but less than the hit of not getting the memory you need at all...
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LEARN ABOUT CENTOS
free_hugepage_region
GET_HUGEPAGE_REGION(3) Library Functions Manual 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);
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 spec-
ify 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) , 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)