malloc: Add Huge Page support to arenas

It is enabled as default for glibc.malloc.hugetlb set to 2 or higher.
It also uses a non configurable minimum value and maximum value,
currently set respectively to 1 and 4 selected huge page size.

The arena allocation with huge pages does not use MAP_NORESERVE.  As
indicate by kernel internal documentation [1], the flag might trigger
a SIGBUS on soft page faults if at memory access there is no left
pages in the pool.

On systems without a reserved huge pages pool, is just stress the
mmap(MAP_HUGETLB) allocation failure.  To improve test coverage it is
required to create a pool with some allocated pages.

Checked on x86_64-linux-gnu with no reserved pages, 10 reserved pages
(which trigger mmap(MAP_HUGETBL) failures) and with 256 reserved pages
(which does not trigger mmap(MAP_HUGETLB) failures).

[1] https://www.kernel.org/doc/html/v4.18/vm/hugetlbfs_reserv.html#resv-map-modifications

Reviewed-by: DJ Delorie <dj@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/malloc/malloc.c b/malloc/malloc.c
index 75efdc2ee7..1698d45d1e 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -5302,7 +5302,7 @@ static __always_inline int
 do_set_mmap_threshold (size_t value)
 {
   /* Forbid setting the threshold too high.  */
-  if (value <= HEAP_MAX_SIZE / 2)
+  if (value <= heap_max_size () / 2)
     {
       LIBC_PROBE (memory_mallopt_mmap_threshold, 3, value, mp_.mmap_threshold,
 		  mp_.no_dyn_threshold);