[PATCH v2 4/4] loongarch: Enable THP-aligned load segments by default and define THP page size

[WANG Rui]

On LoongArch64 Linux, aligning ELF load segments to Transparent Huge Page
(THP) boundaries provides consistent performance benefits for large
binaries by reducing TLB pressure and improving instruction fetch
efficiency.

Enable THP-based load segment alignment by default on LoongArch64 by
defining `DL_MAP_SEGMENT_ALIGN_THP_DEFAULT`. This allows the dynamic
loader to apply THP-friendly alignment without requiring the
`glibc.malloc.hugetlb` tunable to be explicitly set.

Define the default THP page size as 32MB for LoongArch64, reflecting the
architecture’s normal 16KB page size and PMD-level huge page geometry.
This value is used by the THP infrastructure to determine appropriate
alignment and mapping decisions.

* sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h:
Enable THP-based load segment alignment by default.
* sysdeps/unix/sysv/linux/loongarch/lp64/malloc-hugepages.h:
Define the default THP page size.

Signed-off-by: WANG Rui <wangrui@loongson.cn>
---
 elf/tst-decorate-maps.c                       |  2 +-
 .../loongarch/lp64/dl-map-segment-align.h     | 23 +++++++++++++++++++
 .../linux/loongarch/lp64/malloc-hugepages.h   | 21 +++++++++++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h
 create mode 100644 sysdeps/unix/sysv/linux/loongarch/lp64/malloc-hugepages.h

diff --git a/elf/tst-decorate-maps.c b/elf/tst-decorate-maps.c
index fa3637af89..d3e6a5540f 100644
--- a/elf/tst-decorate-maps.c
+++ b/elf/tst-decorate-maps.c
@@ -109,7 +109,7 @@ do_test_threads (bool set_guard)
   xpthread_barrier_init (&b, NULL, num_threads + 1);
 
   /* Issue a large malloc to trigger a mmap call.  */
-  void *p = xmalloc (2 * 1024 * 1024);
+  void *p = xmalloc (32 * 1024 * 1024);
 
   pthread_t thr[num_threads];
   {
diff --git a/sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h b/sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h
new file mode 100644
index 0000000000..8e95419b1c
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h
@@ -0,0 +1,23 @@
+/* _dl_map_segment_align.  LoongArch64 Linux version.
+   Copyright (C) 2026 Free Software Foundation, Inc.
+   Copyright The GNU Toolchain Authors.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* Enable THP-based load segment alignment by default. */
+#define DL_MAP_SEGMENT_ALIGN_THP_DEFAULT 1
+
+#include_next <dl-map-segment-align.h>
diff --git a/sysdeps/unix/sysv/linux/loongarch/lp64/malloc-hugepages.h b/sysdeps/unix/sysv/linux/loongarch/lp64/malloc-hugepages.h
new file mode 100644
index 0000000000..8409670c7c
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/loongarch/lp64/malloc-hugepages.h
@@ -0,0 +1,21 @@
+/* Huge Page support.  LoongArch64 Linux version.
+   Copyright (C) 2026 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If
+   not, see <https://www.gnu.org/licenses/>.  */
+
+#define DEFAULT_THP_PAGESIZE	(32 * 1024 * 1024)
+
+#include_next <malloc-hugepages.h>
-- 
2.53.0