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

[Xi Ruoyao]

On Thu, 2026-03-05 at 20:00 +0800, caiyinyu wrote:
>  
> 
>  
>  
> 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?

See https://github.com/loongson-community/discussions/issues/115.


-- 
Xi Ruoyao <xry111@xry111.site>