Re: [PATCH v5 1/7] malloc: Add madvise support for Transparent Huge Pages

[DJ Delorie <dj@redhat.com>]

Minor tweaks to a comment but otherwise LGTM
Reviewed-by: DJ Delorie <dj@redhat.com>

Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org> writes:
> +* On Linux, a new tunable, glibc.malloc.hugetlb, can be used to
> +  make malloc issue madvise plus MADV_HUGEPAGE on mmap and sbrk calls.
> +  It might improve performance with Transparent Huge Pages madvise mode
> +  depending of the workload.

Suggest replacing "It" with "Setting this" but it's just NEWS.  Ok.

> diff --git a/Rules b/Rules
> @@ -157,6 +157,7 @@ tests: $(tests:%=$(objpfx)%.out) $(tests-internal:%=$(objpfx)%.out) \
>         $(tests-container:%=$(objpfx)%.out) \
>         $(tests-mcheck:%=$(objpfx)%-mcheck.out) \
>         $(tests-malloc-check:%=$(objpfx)%-malloc-check.out) \
> +       $(tests-malloc-hugetlb1:%=$(objpfx)%-malloc-hugetlb1.out) \

Ok.

>  tests-expected = $(tests) $(tests-internal) $(tests-printers) \
>  	$(tests-container) $(tests-malloc-check:%=%-malloc-check) \
> +	$(tests-malloc-hugetlb1:%=%-malloc-hugetlb1) \
>  	$(tests-mcheck:%=%-mcheck)

Ok.

> +binaries-malloc-hugetlb1-tests = $(tests-malloc-hugetlb1:%=%-malloc-hugetlb1)

Ok.

> +binaries-malloc-hugetlb1-tests =

Ok.

> +ifneq "$(strip $(binaries-malloc-hugetlb1-tests))" ""
> +$(addprefix $(objpfx),$(binaries-malloc-hugetlb1-tests)): %-malloc-hugetlb1: %.o \
> +  $(link-extra-libs-tests) \
> +  $(sort $(filter $(common-objpfx)lib%,$(link-libc))) \
> +  $(addprefix $(csu-objpfx),start.o) $(+preinit) $(+postinit)
> +	$(+link-tests)
> +endif

Adds build rules for new targets, ok.

> +# All malloc-hugetlb1 tests will be run with GLIBC_TUNABLE=glibc.malloc.hugetlb=1
> +define malloc-hugetlb1-ENVS
> +$(1)-malloc-hugetlb1-ENV += GLIBC_TUNABLES=glibc.malloc.hugetlb=1
> +endef
> +$(foreach t,$(tests-malloc-hugetlb1),$(eval $(call malloc-hugetlb1-ENVS,$(t))))

Ok.


> diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list
> +    hugetlb {
> +      type: INT_32
> +      minval: 0
> +      maxval: 1
> +    }

Ok.

> diff --git a/elf/tst-rtld-list-tunables.exp b/elf/tst-rtld-list-tunables.exp
> +glibc.malloc.hugetlb: 0 (min: 0, max: 1)

Ok.

> diff --git a/malloc/Makefile b/malloc/Makefile
>  
> +# Run all testes with GLIBC_TUNABLE=glibc.malloc.hugetlb=1 that check the
> +# Transparent Huge Pages support.  We need exclude some tests that define
> +# the ENV vars.
> +tests-exclude-hugetlb1 = \
> +	tst-compathooks-off \
> +	tst-compathooks-on \
> +	tst-interpose-nothread \
> +	tst-interpose-thread \
> +	tst-interpose-static-nothread \
> +	tst-interpose-static-thread \
> +	tst-malloc-usable \
> +	tst-malloc-usable-tunables \
> +	tst-mallocstate
> +tests-malloc-hugetlb1 = \
> +	$(filter-out $(tests-exclude-hugetlb1), $(tests))

Ok.

> diff --git a/malloc/arena.c b/malloc/arena.c
> +TUNABLE_CALLBACK_FNDECL (set_hugetlb, int32_t)

Ok.

> +  TUNABLE_GET (hugetlb, int32_t, TUNABLE_CALLBACK (set_hugetlb));

Ok.

> @@ -508,6 +510,9 @@ new_heap (size_t size, size_t top_pad)
> +
> +  madvise_thp (p2, size);

Ok.

> diff --git a/malloc/malloc-internal.h b/malloc/malloc-internal.h
> +#include <malloc-hugepages.h>

Ok.

> diff --git a/malloc/malloc.c b/malloc/malloc.c
> +#if HAVE_TUNABLES
> +  /* Transparent Large Page support.  */
> +  INTERNAL_SIZE_T thp_pagesize;
> +#endif

Ok.

> @@ -2008,6 +2013,20 @@ free_perturb (char *p, size_t n)
> +/* ----------- Routines dealing with transparent huge pages ----------- */
> +
> +static inline void
> +madvise_thp (void *p, INTERNAL_SIZE_T size)
> +{
> +#if HAVE_TUNABLES && defined (MADV_HUGEPAGE)
> +  /* Do not consider areas smaller than a huge page or if the tunable is
> +     not active.  */
> +  if (mp_.thp_pagesize == 0 || size < mp_.thp_pagesize)
> +    return;
> +  __madvise (p, size, MADV_HUGEPAGE);
> +#endif
> +}

Ok.

> +	      madvise_thp (mm, size);

Ok.

>        if (size > 0)
>          {
>            brk = (char *) (MORECORE (size));
> +	  if (brk != (char *) (MORECORE_FAILURE))
> +	    madvise_thp (brk, size);
>            LIBC_PROBE (memory_sbrk_more, 2, brk, size);
>          }

Ok.

>                if (mbrk != MAP_FAILED)
>                  {
> +		  madvise_thp (mbrk, size);

Ok.

> +		  else
> +		    madvise_thp (snd_brk, correction);

Ok.

> @@ -2988,6 +3015,8 @@ mremap_chunk (mchunkptr p, size_t new_size)
>    if (cp == MAP_FAILED)
>      return 0;
>  
> +  madvise_thp (cp, new_size);

Ok.

> +#if HAVE_TUNABLES
> +static __always_inline int
> +do_set_hugetlb (int32_t value)
> +{
> +  if (value == 1)
> +    {
> +      enum malloc_thp_mode_t thp_mode = __malloc_thp_mode ();
> +      /*
> +	 Only enables THP usage is system does support it and has at least
> +	 always or madvise mode.  Otherwise the madvise() call is wasteful.
> +       */
> +      if (thp_mode == malloc_thp_mode_madvise)
> +	mp_.thp_pagesize = __malloc_default_thp_pagesize ();
> +    }
> +  return 0;
> +}
> +#endif

s/is/if/

The "always or madvise mode" comment doesn't match the "== madvise"
logic.  I suspect the logic is ok, so... ok with fixed comment.

> diff --git a/manual/tunables.texi b/manual/tunables.texi
> +@deftp Tunable glibc.malloc.hugetlb
> +This tunable controls the usage of Huge Pages on @code{malloc} calls.  The
> +default value is @code{0}, which disables any additional support on
> +@code{malloc}.
> +
> +Setting its value to @code{1} enables the use of @code{madvise} with
> +@code{MADV_HUGEPAGE} after memory allocation with @code{mmap}.  It is enabled
> +only if the system supports Transparent Huge Page (currently only on Linux).
> +@end deftp

Ok.

> diff --git a/sysdeps/generic/Makefile b/sysdeps/generic/Makefile
> +ifeq ($(subdir),malloc)
> +sysdep_malloc_debug_routines += malloc-hugepages
> +endif
> +
> +ifeq ($(subdir),misc)
> +sysdep_routines += malloc-hugepages
> +endif

Ok.

> diff --git a/sysdeps/generic/malloc-hugepages.c b/sysdeps/generic/malloc-hugepages.c
> +/* Huge Page support.  Generic implementation.
> +   Copyright (C) 2021 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/>.  */
> +
> +#include <malloc-hugepages.h>
> +
> +unsigned long int
> +__malloc_default_thp_pagesize (void)
> +{
> +  return 0;
> +}
> +
> +enum malloc_thp_mode_t
> +__malloc_thp_mode (void)
> +{
> +  return malloc_thp_mode_not_supported;
> +}

Ok.

> diff --git a/sysdeps/generic/malloc-hugepages.h b/sysdeps/generic/malloc-hugepages.h
> +/* Malloc huge page support.  Generic implementation.
> +   Copyright (C) 2021 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/>.  */
> +
> +#ifndef _MALLOC_HUGEPAGES_H
> +#define _MALLOC_HUGEPAGES_H
> +
> +#include <stddef.h>
> +
> +/* Return the default transparent huge page size.  */
> +unsigned long int __malloc_default_thp_pagesize (void) attribute_hidden;
> +
> +enum malloc_thp_mode_t
> +{
> +  malloc_thp_mode_always,
> +  malloc_thp_mode_madvise,
> +  malloc_thp_mode_never,
> +  malloc_thp_mode_not_supported
> +};
> +
> +enum malloc_thp_mode_t __malloc_thp_mode (void) attribute_hidden;
> +
> +#endif /* _MALLOC_HUGEPAGES_H */

Ok.

> diff --git a/sysdeps/unix/sysv/linux/malloc-hugepages.c b/sysdeps/unix/sysv/linux/malloc-hugepages.c
> +/* Huge Page support.  Linux implementation.
> +   Copyright (C) 2021 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/>.  */
> +
> +#include <intprops.h>
> +#include <malloc-hugepages.h>
> +#include <not-cancel.h>
> +

Ok.

> +unsigned long int
> +__malloc_default_thp_pagesize (void)
> +{
> +  int fd = __open64_nocancel (
> +    "/sys/kernel/mm/transparent_hugepage/hpage_pmd_size", O_RDONLY);
> +  if (fd == -1)
> +    return 0;
> +
> +  char str[INT_BUFSIZE_BOUND (unsigned long int)];
> +  ssize_t s = __read_nocancel (fd, str, sizeof (str));
> +  __close_nocancel (fd);
> +  if (s < 0)
> +    return 0;
> +
> +  unsigned long int r = 0;
> +  for (ssize_t i = 0; i < s; i++)
> +    {
> +      if (str[i] == '\n')
> +	break;
> +      r *= 10;
> +      r += str[i] - '0';
> +    }
> +  return r;
> +}

Ok.

> +enum malloc_thp_mode_t
> +__malloc_thp_mode (void)
> +{
> +  int fd = __open64_nocancel ("/sys/kernel/mm/transparent_hugepage/enabled",
> +			      O_RDONLY);
> +  if (fd == -1)
> +    return malloc_thp_mode_not_supported;
> +
> +  static const char mode_always[]  = "[always] madvise never\n";
> +  static const char mode_madvise[] = "always [madvise] never\n";
> +  static const char mode_never[]   = "always madvise [never]\n";
> +
> +  char str[sizeof(mode_always)];
> +  ssize_t s = __read_nocancel (fd, str, sizeof (str));
> +  __close_nocancel (fd);
> +
> +  if (s == sizeof (mode_always) - 1)
> +    {
> +      if (strcmp (str, mode_always) == 0)
> +	return malloc_thp_mode_always;
> +      else if (strcmp (str, mode_madvise) == 0)
> +	return malloc_thp_mode_madvise;
> +      else if (strcmp (str, mode_never) == 0)
> +	return malloc_thp_mode_never;
> +    }
> +  return malloc_thp_mode_not_supported;
> +}

Ok.