benchtests: Add memset zero fill benchmark tests

  Memset takes 0 as the second parameter in most cases.
More than 95% of memset takes 0 as the second parameter in case of
Linux Kernel source code.
However, we cannot measure the zero fill performance by
bench-memset-zerofill.c and bench-memset-large-zerofill.c.
This patch provides bench-memset-zerofill.c and
bench-memset-large-zerofill.c which are suitable to see the
performance of zero fill by fixing the second parameter to 0.
---
 benchtests/Makefile                      |   3 +-
 benchtests/bench-memset-large-zerofill.c | 125 ++++++++++++++++++
 benchtests/bench-memset-zerofill.c       | 156 +++++++++++++++++++++++
 3 files changed, 283 insertions(+), 1 deletion(-)
 create mode 100644 benchtests/bench-memset-large-zerofill.c
 create mode 100644 benchtests/bench-memset-zerofill.c
  

Hi Naohiro,
Thanks for working on this.

I like the idea of a benchmark specific for 0 on memset. However having two
implementations seems too much. I would rather see just one
bench-memset-zerofill.c. What I guess would be even better is to have this
performance test inside bench-memset.c and bench-memset-large.c.

Quoting Naohiro Tamura via Libc-alpha (2021-07-13 05:22:14)
> Memset takes 0 as the second parameter in most cases.
> More than 95% of memset takes 0 as the second parameter in case of
> Linux Kernel source code.
The Linux Kernel does not use glibc, it has his own memset implementation.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/lib/string.c#n784
Therefore IMO this argument is not suited for this commit.

> However, we cannot measure the zero fill performance by
> bench-memset-zerofill.c and bench-memset-large-zerofill.c.
> This patch provides bench-memset-zerofill.c and
> bench-memset-large-zerofill.c which are suitable to see the
> performance of zero fill by fixing the second parameter to 0.
In this section I guess you mistake bench-memset.c and bench-memset-large.c for
bench-memset-zerofill.c and bench-memset-large-zerofill.c.

> ---
>  benchtests/Makefile                      |   3 +-
>  benchtests/bench-memset-large-zerofill.c | 125 ++++++++++++++++++
>  benchtests/bench-memset-zerofill.c       | 156 +++++++++++++++++++++++
>  3 files changed, 283 insertions(+), 1 deletion(-)
>  create mode 100644 benchtests/bench-memset-large-zerofill.c
>  create mode 100644 benchtests/bench-memset-zerofill.c
> 
> diff --git a/benchtests/Makefile b/benchtests/Makefile
> index 1530939a8ce8..1261f7650fc7 100644
> --- a/benchtests/Makefile
> +++ b/benchtests/Makefile
> @@ -53,7 +53,8 @@ string-benchset := memccpy memchr memcmp memcpy memmem memmove \
>                    strncasecmp strncat strncmp strncpy strnlen strpbrk strrchr \
>                    strspn strstr strcpy_chk stpcpy_chk memrchr strsep strtok \
>                    strcoll memcpy-large memcpy-random memmove-large memset-large \
> -                  memcpy-walk memset-walk memmove-walk
> +                  memcpy-walk memset-walk memmove-walk memset-zerofill \
> +                  memset-large-zerofill
>  
>  # Build and run locale-dependent benchmarks only if we're building natively.
>  ifeq (no,$(cross-compiling))
> diff --git a/benchtests/bench-memset-large-zerofill.c b/benchtests/bench-memset-large-zerofill.c
> new file mode 100644
> index 000000000000..d8eae9d9789f
> --- /dev/null
> +++ b/benchtests/bench-memset-large-zerofill.c
> @@ -0,0 +1,125 @@
> +/* Measure memset functions with large data sizes.
Please fix this description.

> +   Copyright (C) 2016-2021 Free Software Foundation, Inc.
Just 2021 here.

> +   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 TEST_MAIN
> +#define TEST_NAME "memset"
> +#define START_SIZE (128 * 1024)
> +#define MIN_PAGE_SIZE (getpagesize () + 64 * 1024 * 1024)
> +#define TIMEOUT (20 * 60)
> +#include "bench-string.h"
> +
> +#include <assert.h>
> +#include "json-lib.h"
> +
This code don't need the assert.h.

> +void *generic_memset (void *, int, size_t);
> +typedef void *(*proto_t) (void *, int, size_t);
> +
> +IMPL (MEMSET, 1)
> +IMPL (generic_memset, 0)
> +
> +static void
> +do_one_test (json_ctx_t *json_ctx, impl_t *impl, CHAR *s,
> +            int c __attribute ((unused)), size_t n)
> +{
> +  size_t i, iters = 16;
> +  timing_t start, stop, cur;
> +
> +  TIMING_NOW (start);
> +  for (i = 0; i < iters; ++i)
> +    {
> +      CALL (impl, s, c, n);
> +    }
> +  TIMING_NOW (stop);
> +
> +  TIMING_DIFF (cur, start, stop);
> +
> +  json_element_double (json_ctx, (double) cur / (double) iters);
> +}
> +
> +static void
> +do_test (json_ctx_t *json_ctx, size_t align, int c, size_t len)
> +{
> +  align &= 63;
> +  if ((align + len) * sizeof (CHAR) > page_size)
> +    return;
> +
> +  json_element_object_begin (json_ctx);
> +  json_attr_uint (json_ctx, "length", len);
> +  json_attr_uint (json_ctx, "alignment", align);
> +  json_attr_int (json_ctx, "char", c);
> +  json_array_begin (json_ctx, "timings");
> +
> +  FOR_EACH_IMPL (impl, 0)
> +    {
> +      do_one_test (json_ctx, impl, (CHAR *) (buf1) + align, c, len);
> +      alloc_bufs ();
> +    }
> +
> +  json_array_end (json_ctx);
> +  json_element_object_end (json_ctx);
> +}
> +
> +int
> +test_main (void)
> +{
> +  json_ctx_t json_ctx;
> +  size_t i;
> +  int c;
> +
> +  test_init ();
> +
> +  json_init (&json_ctx, 0, stdout);
> +
> +  json_document_begin (&json_ctx);
> +  json_attr_string (&json_ctx, "timing_type", TIMING_TYPE);
> +
> +  json_attr_object_begin (&json_ctx, "functions");
> +  json_attr_object_begin (&json_ctx, TEST_NAME);
> +  json_attr_string (&json_ctx, "bench-variant", "large-zerofill");
> +
> +  json_array_begin (&json_ctx, "ifuncs");
> +  FOR_EACH_IMPL (impl, 0)
> +    json_element_string (&json_ctx, impl->name);
> +  json_array_end (&json_ctx);
> +
> +  json_array_begin (&json_ctx, "results");
> +
> +  c = 0;
> +  for (i = START_SIZE; i <= MIN_PAGE_SIZE; i <<= 1)
> +    {
> +      do_test (&json_ctx, 0, c, i);
> +      do_test (&json_ctx, 3, c, i);
> +    }
> +
> +  json_array_end (&json_ctx);
> +  json_attr_object_end (&json_ctx);
> +  json_attr_object_end (&json_ctx);
> +  json_document_end (&json_ctx);
> +
> +  return ret;
> +}
> +
> +#include <support/test-driver.c>
> +
> +#define libc_hidden_builtin_def(X)
> +#define libc_hidden_def(X)
> +#define libc_hidden_weak(X)
> +#define weak_alias(X,Y)
> +#undef MEMSET
> +#define MEMSET generic_memset
> +#include <string/memset.c>
> diff --git a/benchtests/bench-memset-zerofill.c b/benchtests/bench-memset-zerofill.c
> new file mode 100644
> index 000000000000..ac20ae4c6537
> --- /dev/null
> +++ b/benchtests/bench-memset-zerofill.c
> @@ -0,0 +1,156 @@
> +/* Measure memset functions.
Fix the description.

> +   Copyright (C) 2013-2021 Free Software Foundation, Inc.
Only 2021 here.

> +   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 TEST_MAIN
> +#ifndef WIDE
> +# define TEST_NAME "memset"
> +#else
> +# define TEST_NAME "wmemset"
> +# define generic_memset generic_wmemset
> +#endif /* WIDE */
> +#define MIN_PAGE_SIZE 131072
> +#include "bench-string.h"
> +
> +#include "json-lib.h"
> +
> +#ifdef WIDE
> +CHAR *generic_wmemset (CHAR *, CHAR, size_t);
> +#else
> +void *generic_memset (void *, int, size_t);
> +#endif
> +
> +typedef void *(*proto_t) (void *, int, size_t);
> +
> +IMPL (MEMSET, 1)
> +IMPL (generic_memset, 0)
> +
> +static void
> +do_one_test (json_ctx_t *json_ctx, impl_t *impl, CHAR *s,
> +            int c __attribute ((unused)), size_t n)
> +{
> +  size_t i, iters = INNER_LOOP_ITERS;
> +  timing_t start, stop, cur;
> +
> +  TIMING_NOW (start);
> +  for (i = 0; i < iters; ++i)
> +    {
> +      CALL (impl, s, c, n);
> +    }
> +  TIMING_NOW (stop);
> +
> +  TIMING_DIFF (cur, start, stop);
> +
> +  json_element_double (json_ctx, (double) cur / (double) iters);
> +}
> +
> +static void
> +do_test (json_ctx_t *json_ctx, size_t align, int c, size_t len)
> +{
> +  align &= 4095;
> +  if ((align + len) * sizeof (CHAR) > page_size)
> +    return;
> +
> +  json_element_object_begin (json_ctx);
> +  json_attr_uint (json_ctx, "length", len);
> +  json_attr_uint (json_ctx, "alignment", align);
> +  json_attr_int (json_ctx, "char", c);
> +  json_array_begin (json_ctx, "timings");
> +
> +  FOR_EACH_IMPL (impl, 0)
> +    {
> +      do_one_test (json_ctx, impl, (CHAR *) (buf1) + align, c, len);
> +      alloc_bufs ();
> +    }
> +
> +  json_array_end (json_ctx);
> +  json_element_object_end (json_ctx);
> +}
> +
> +int
> +test_main (void)
> +{
> +  json_ctx_t json_ctx;
> +  size_t i;
> +  int c = 0;
> +
> +  test_init ();
> +
> +  json_init (&json_ctx, 0, stdout);
> +
> +  json_document_begin (&json_ctx);
> +  json_attr_string (&json_ctx, "timing_type", TIMING_TYPE);
> +
> +  json_attr_object_begin (&json_ctx, "functions");
> +  json_attr_object_begin (&json_ctx, TEST_NAME);
> +  json_attr_string (&json_ctx, "bench-variant", "default-zerofill");
> +
> +  json_array_begin (&json_ctx, "ifuncs");
> +  FOR_EACH_IMPL (impl, 0)
> +    json_element_string (&json_ctx, impl->name);
> +  json_array_end (&json_ctx);
> +
> +  json_array_begin (&json_ctx, "results");
> +
> +  c = 0;
> +  for (i = 0; i < 18; ++i)
> +    do_test (&json_ctx, 0, c, 1 << i);
> +  for (i = 1; i < 64; ++i)
> +    {
> +      do_test (&json_ctx, i, c, i);
> +      do_test (&json_ctx, 4096 - i, c, i);
> +      do_test (&json_ctx, 4095, c, i);
> +      if (i & (i - 1))
> +       do_test (&json_ctx, 0, c, i);
> +    }
> +  for (i = 32; i < 512; i+=32)
> +    {
> +      do_test (&json_ctx, 0, c, i);
> +      do_test (&json_ctx, i, c, i);
> +    }
> +  do_test (&json_ctx, 1, c, 14);
> +  do_test (&json_ctx, 3, c, 1024);
> +  do_test (&json_ctx, 4, c, 64);
> +  do_test (&json_ctx, 2, c, 25);
> +  for (i = 33; i <= 256; i += 4)
> +    {
> +      do_test (&json_ctx, 0, c, 32 * i);
> +      do_test (&json_ctx, i, c, 32 * i);
> +    }
> +
> +  json_array_end (&json_ctx);
> +  json_attr_object_end (&json_ctx);
> +  json_attr_object_end (&json_ctx);
> +  json_document_end (&json_ctx);
> +
> +  return ret;
> +}
> +
> +#include <support/test-driver.c>
> +
> +#define libc_hidden_builtin_def(X)
> +#define libc_hidden_def(X)
> +#define libc_hidden_weak(X)
> +#define weak_alias(X,Y)
> +#ifndef WIDE
> +# undef MEMSET
> +# define MEMSET generic_memset
> +# include <string/memset.c>
> +#else
> +# define WMEMSET generic_wmemset
> +# include <wcsmbs/wmemset.c>
> +#endif
> -- 
> 2.17.1
> 

---
Lucas A. M. Magalhães