Eric,

Eric B Munson wrote:
> As with get_huge_pages it is appropriate to use MAP_HUGETLB for
> mappings that will hold the heap.
> 
> Signed-off-by: Eric B Munson <[email protected]>
> ---
>  morecore.c |   31 +++++++++++++++++++++----------
>  1 files changed, 21 insertions(+), 10 deletions(-)
> 
> diff --git a/morecore.c b/morecore.c
> index e120d55..4fd51c3 100644
> --- a/morecore.c
> +++ b/morecore.c
> @@ -94,8 +94,13 @@ static void *hugetlbfs_morecore(ptrdiff_t increment)
>               INFO("Attempting to map %ld bytes\n", delta);
>  
>               /* map in (extend) more of the file at the end of our last map 
> */
> -             p = mmap(heapbase + mapsize, delta, PROT_READ|PROT_WRITE,
> -                      MAP_PRIVATE|mmap_reserve, heap_fd, mapsize);
> +             if (__hugetlb_opts.map_hugetlb)
> +                     p = mmap(heapbase + mapsize, delta, 
> PROT_READ|PROT_WRITE,
> +                              
> MAP_HUGETLB|MAP_ANONYMOUS|MAP_PRIVATE|mmap_reserve,
> +                              heap_fd, mapsize);
> +             else
> +                     p = mmap(heapbase + mapsize, delta, 
> PROT_READ|PROT_WRITE,
> +                              MAP_PRIVATE|mmap_reserve, heap_fd, mapsize);
>               if (p == MAP_FAILED) {
>                       WARNING("New heap segment map at %p failed: %s\n",
>                               heapbase+mapsize, strerror(errno));
> @@ -166,7 +171,7 @@ static void *hugetlbfs_morecore(ptrdiff_t increment)
>               if (ret) {
>                       WARNING("Unmapping failed while shrinking heap: "
>                               "%s\n", strerror(errno));
> -             } else {
> +             } else if (!__hugetlb_opts.map_hugetlb){
>  
>                       /*
>                        * Now shrink the hugetlbfs file.
> @@ -223,15 +228,21 @@ void hugetlbfs_setup_morecore(void)
>               else
>                       WARNING("Hugepage size (%s)\n", strerror(errno));
>               return;
> -     } else if (!hugetlbfs_find_path_for_size(hpage_size)) {
> -             WARNING("Hugepage size %li unavailable", hpage_size);
> -             return;
>       }
>  
> -     heap_fd = hugetlbfs_unlinked_fd_for_size(hpage_size);
> -     if (heap_fd < 0) {
> -             WARNING("Couldn't open hugetlbfs file for morecore\n");
> -             return;
> +     if(__hugetlb_opts.map_hugetlb) {
> +             heap_fd = -1;
> +     } else {
> +             if (!hugetlbfs_find_path_for_size(hpage_size)) {
> +                     WARNING("Hugepage size %li unavailable", hpage_size);
> +                     return;
> +             }
> +
> +             heap_fd = hugetlbfs_unlinked_fd_for_size(hpage_size);
> +             if (heap_fd < 0) {
> +                     WARNING("Couldn't open hugetlbfs file for morecore\n");
> +                     return;
> +             }
>       }
>  
>       if (__hugetlb_opts.heapbase) {

If the kernel supports MAP_HUGETLB, won't this code ignore the user's requested 
hugepage size?  We have users that depend on the ability to specify the 
hugepage size.

Perhaps use MAP_HUGETLB for the heap only if the user's requested hugepage size 
matches the kernel default hugepage size?

-Andrew Hastings
 Cray Inc.

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