[glibc] malloc: Enable huge page support on main arena

[glibc] malloc: Enable huge page support on main arena

[Adhemerval Zanella]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=0f982c182760bd7689769ee7590df592d0a132c0

commit 0f982c182760bd7689769ee7590df592d0a132c0
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Mon Aug 30 14:01:00 2021 -0300

    malloc: Enable huge page support on main arena
    
    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.
    
    Reviewed-by: DJ Delorie <dj@redhat.com>

Diff:
---
 malloc/arena.c    |  4 ++++
 malloc/malloc.c   | 12 ++++++++++--
 malloc/morecore.c |  4 ----
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/malloc/arena.c b/malloc/arena.c
index e1852f8597..3ed4ef3f05 100644
--- a/malloc/arena.c
+++ b/malloc/arena.c
@@ -364,6 +364,10 @@ ptmalloc_init (void)
 # endif
   TUNABLE_GET (mxfast, size_t, TUNABLE_CALLBACK (set_mxfast));
   TUNABLE_GET (hugetlb, size_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 32050be4cc..b67f2c84ee 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -2741,8 +2741,16 @@ 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..004cd3ead4 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.
@@ -25,10 +23,8 @@ static bool __always_fail_morecore = false;
 void *
 __glibc_morecore (ptrdiff_t increment)
 {
-#if defined(SHARED) || defined(USE_MTAG)
   if (__always_fail_morecore)
     return NULL;
-#endif
 
   void *result = (void *) __sbrk (increment);
   if (result == (void *) -1)