[PATCH v4 7/7] malloc: Enable huge page support on main arena

[Adhemerval Zanella]

This patch adds support huge page support on main arena allocation,
enable with tunable glibc.malloc.hugetlb=2.  The patch essentially
disable the __glibc_morecore() sbrk() call (similar when memory
tag does when sbrk() call does not support it) and fallback to
default page size if the memory allocation fails.

Checked on x86_64-linux-gnu.
---
 malloc/arena.c    |  4 ++++
 malloc/malloc.c   | 12 ++++++++++--
 malloc/morecore.c |  2 --
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/malloc/arena.c b/malloc/arena.c
index 81dc2f93d1..0d38cad9b8 100644
--- a/malloc/arena.c
+++ b/malloc/arena.c
@@ -357,6 +357,10 @@ ptmalloc_init (void)
 # endif
   TUNABLE_GET (mxfast, size_t, TUNABLE_CALLBACK (set_mxfast));
   TUNABLE_GET (hugetlb, int32_t, TUNABLE_CALLBACK (set_hugetlb));
+  if (mp_.hp_pagesize > 0)
+    /* Force mmap() for main arena instead of sbrk(), so hugepages are
+       explicitly used.  */
+    __always_fail_morecore = true;
 #else
   if (__glibc_likely (_environ != NULL))
     {
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 3421a0b5da..616aaf9e59 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -2742,8 +2742,16 @@ sysmalloc (INTERNAL_SIZE_T nb, mstate av)
              segregated mmap region.
            */
 
-	  char *mbrk = sysmalloc_mmap_fallback (&size, nb, old_size, pagesize,
-						MMAP_AS_MORECORE_SIZE, 0, av);
+	  char *mbrk = MAP_FAILED;
+#if HAVE_TUNABLES
+	  if (mp_.hp_pagesize > 0)
+	    mbrk = sysmalloc_mmap_fallback (&size, nb, old_size,
+					    mp_.hp_pagesize, mp_.hp_pagesize,
+					    mp_.hp_flags, av);
+#endif
+	  if (mbrk == MAP_FAILED)
+	    mbrk = sysmalloc_mmap_fallback (&size, nb, old_size, pagesize,
+					    MMAP_AS_MORECORE_SIZE, 0, av);
 	  if (mbrk != MAP_FAILED)
 	    {
 	      /* We do not need, and cannot use, another sbrk call to find end */
diff --git a/malloc/morecore.c b/malloc/morecore.c
index 8168ef158c..1ace85a37d 100644
--- a/malloc/morecore.c
+++ b/malloc/morecore.c
@@ -15,9 +15,7 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#if defined(SHARED) || defined(USE_MTAG)
 static bool __always_fail_morecore = false;
-#endif
 
 /* Allocate INCREMENT more bytes of data space,
    and return the start of data space, or NULL on errors.
-- 
2.30.2