[PATCH v4 6/6] loongarch: Enable THP-aligned load segments by default on 64-bit

[caiyinyu]

在 2026/3/5 上午10:58, WANG Rui 写道:
> 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
> setting `glibc.elf.hugetlb=1` during startup. Define the default THP
> page size for load segment alignment on LoongArch64 as 32MB.
>
> This allows the dynamic loader to apply THP-friendly alignment without
> requiring the `glibc.elf.hugetlb` tunable to be explicitly set.
>
> * sysdeps/unix/sysv/linux/loongarch/cpu-features.c
> (init_cpu_features): Set glibc.elf.hugetlb to 1 by default on LoongArch64.
> * sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h:
> Define DL_MAP_DEFAULT_THP_PAGESIZE as 32MB.
>
> Signed-off-by: WANG Rui <wangrui@loongson.cn>
> ---
>   .../unix/sysv/linux/loongarch/cpu-features.c  |  6 +++++
>   .../loongarch/lp64/dl-map-segment-align.h     | 22 +++++++++++++++++++
>   2 files changed, 28 insertions(+)
>   create mode 100644 sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h
>
> diff --git a/sysdeps/unix/sysv/linux/loongarch/cpu-features.c b/sysdeps/unix/sysv/linux/loongarch/cpu-features.c
> index 0c125e64e2b..4da3f1ad4ee 100644
> --- a/sysdeps/unix/sysv/linux/loongarch/cpu-features.c
> +++ b/sysdeps/unix/sysv/linux/loongarch/cpu-features.c
> @@ -27,4 +27,10 @@ init_cpu_features (struct cpu_features *cpu_features)
>     GLRO(dl_larch_cpu_features).hwcap = GLRO(dl_hwcap);
>     TUNABLE_GET (glibc, cpu, hwcaps, tunable_val_t *,
>   	       TUNABLE_CALLBACK (set_hwcaps));
> +
> +#ifdef __LP64__
> +  /* Enable THP-based load segment alignment by default on LoongArch64. */
> +  if (!TUNABLE_IS_INITIALIZED (glibc, elf, hugetlb))
> +    TUNABLE_SET (glibc, elf, hugetlb, 1);
> +#endif
>   }
> 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 00000000000..c51ee4ac47e
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h
> @@ -0,0 +1,22 @@
> +/* _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/>.  */
> +
> +#define DL_MAP_DEFAULT_THP_PAGESIZE (32 * 1024 * 1024)
> +
> +#include_next <dl-map-segment-align.h>

HI, rui, *Any benchmarks on the improvements?*

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