Re: [PATCH v1] Benchtest: Add additional benchmarks for strlen and strnlen

[Sunil Pandey <skpgkp2@gmail.com>]

On Wed, Sep 28, 2022 at 12:20 PM Noah Goldstein via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> Current benchmarks are missing many cases in the mid-length range
> which is often the hottest size range.

How do you know if the mid-length range is the hottest size range?
Can you please share data to back your claim.

> ---
>  benchtests/bench-strlen.c  | 33 ++++++++++++++++++++---
>  benchtests/bench-strnlen.c | 55 +++++++++++++++++++++++++++++++++++---
>  2 files changed, 81 insertions(+), 7 deletions(-)
>
> diff --git a/benchtests/bench-strlen.c b/benchtests/bench-strlen.c
> index 602e52ee83..696e4541d7 100644
> --- a/benchtests/bench-strlen.c
> +++ b/benchtests/bench-strlen.c
> @@ -128,10 +128,10 @@ test_main (void)
>    /* Checking with only 4 * N alignments for wcslen, other alignments are wrong for wchar_t type arrays*/
>
>    for (i = 1; i < 8; ++i)
> -  {
> -    do_test (&json_ctx, sizeof (CHAR) * i, i);
> -    do_test (&json_ctx, 0, i);
> -  }
> +    {
> +      do_test (&json_ctx, sizeof (CHAR) * i, i);
> +      do_test (&json_ctx, 0, i);
> +    }
>
>    for (i = 2; i <= 12; ++i)
>      {
> @@ -141,6 +141,31 @@ test_main (void)
>        do_test (&json_ctx, sizeof (CHAR) * i, (size_t)((1 << i) / 1.5));
>      }
>
> +  for (i = 0; i < 512; i += 32)
> +    {
> +      do_test (&json_ctx, 0, i / sizeof (CHAR));
> +    }
> +
> +  for (i = 512; i < 1024; i += 64)
> +    {
> +      do_test (&json_ctx, 0, i / sizeof (CHAR));
> +    }
> +
> +  for (i = 1024; i < 2048; i += 128)
> +    {
> +      do_test (&json_ctx, 0, i / sizeof (CHAR));
> +    }
> +
> +  for (i = 2048; i < 4096; i += 256)
> +    {
> +      do_test (&json_ctx, 0, i / sizeof (CHAR));
> +    }
> +
> +  for (i = 4096; i < 8192; i += 512)
> +    {
> +      do_test (&json_ctx, 0, i / sizeof (CHAR));
> +    }
> +
>    json_array_end (&json_ctx);
>    json_attr_object_end (&json_ctx);
>    json_attr_object_end (&json_ctx);
> diff --git a/benchtests/bench-strnlen.c b/benchtests/bench-strnlen.c
> index 2cd561dfd5..13b46b3f57 100644
> --- a/benchtests/bench-strnlen.c
> +++ b/benchtests/bench-strnlen.c
> @@ -63,6 +63,11 @@ do_one_test (json_ctx_t *json_ctx, impl_t *impl, const CHAR *s, size_t maxlen,
>        ret = 1;
>        return;
>      }
> +  /* Warmup.  */
> +  for (i = 0; i < iters / 16; ++i)
> +    {
> +      CALL (impl, s, maxlen);
> +    }
>
>    TIMING_NOW (start);
>    for (i = 0; i < iters; ++i)
> @@ -110,7 +115,7 @@ do_test (json_ctx_t *json_ctx, size_t align, size_t len, size_t maxlen,
>  int
>  test_main (void)
>  {
> -  size_t i;
> +  size_t i, j;
>    json_ctx_t json_ctx;
>
>    test_init ();
> @@ -131,6 +136,19 @@ test_main (void)
>
>    json_array_begin (&json_ctx, "results");
>
> +  for (i = 0; i <= 1; ++i)
> +    {
> +      do_test (&json_ctx, i, 1, 128, MIDDLE_CHAR);
> +      do_test (&json_ctx, i, 128, 1, MIDDLE_CHAR);
> +      do_test (&json_ctx, i, 1, 2, MIDDLE_CHAR);
> +      do_test (&json_ctx, i, 2, 1, MIDDLE_CHAR);
> +
> +      do_test (&json_ctx, 32 + i, 1, 128, MIDDLE_CHAR);
> +      do_test (&json_ctx, 32 + i, 128, 1, MIDDLE_CHAR);
> +      do_test (&json_ctx, 32 + i, 1, 2, MIDDLE_CHAR);
> +      do_test (&json_ctx, 32 + i, 2, 1, MIDDLE_CHAR);
> +    }
> +
>    for (i = 1; i < 8; ++i)
>      {
>        do_test (&json_ctx, 0, i, i - 1, MIDDLE_CHAR);
> @@ -149,18 +167,49 @@ test_main (void)
>      {
>        do_test (&json_ctx, 0, 1 << i, 5000, MIDDLE_CHAR);
>        do_test (&json_ctx, 1, 1 << i, 5000, MIDDLE_CHAR);
> +      do_test (&json_ctx, 0, 5000, 1 << i, MIDDLE_CHAR);
> +      do_test (&json_ctx, 1, 5000, 1 << i, MIDDLE_CHAR);
>      }
>
>    for (i = 1; i < 8; ++i)
> -    do_test (&json_ctx, 0, i, 5000, BIG_CHAR);
> +    {
> +      do_test (&json_ctx, 0, i, 5000, BIG_CHAR);
> +      do_test (&json_ctx, 0, 5000, i, BIG_CHAR);
> +    }
>
>    for (i = 1; i < 8; ++i)
> -    do_test (&json_ctx, i, i, 5000, BIG_CHAR);
> +    {
> +      do_test (&json_ctx, i, i, 5000, BIG_CHAR);
> +      do_test (&json_ctx, i, 5000, i, BIG_CHAR);
> +    }
>
>    for (i = 2; i <= 10; ++i)
>      {
>        do_test (&json_ctx, 0, 1 << i, 5000, BIG_CHAR);
>        do_test (&json_ctx, 1, 1 << i, 5000, BIG_CHAR);
> +      do_test (&json_ctx, 0, 5000, 1 << i, BIG_CHAR);
> +      do_test (&json_ctx, 1, 5000, 1 << i, BIG_CHAR);
> +    }
> +
> +  for (i = (16 / sizeof (CHAR)); i <= (8192 / sizeof (CHAR)); i += i)
> +    {
> +      for (j = 0; j <= (704 / sizeof (CHAR)); j += (32 / sizeof (CHAR)))
> +       {
> +         do_test (&json_ctx, 0, 1 << i, (i + j), BIG_CHAR);
> +         do_test (&json_ctx, 0, i + j, i, BIG_CHAR);
> +
> +         do_test (&json_ctx, 64, 1 << i, (i + j), BIG_CHAR);
> +         do_test (&json_ctx, 64, i + j, i, BIG_CHAR);
> +
> +         if (j < i)
> +           {
> +             do_test (&json_ctx, 0, 1 << i, i - j, BIG_CHAR);
> +             do_test (&json_ctx, 0, i - j, i, BIG_CHAR);
> +
> +             do_test (&json_ctx, 64, 1 << i, i - j, BIG_CHAR);
> +             do_test (&json_ctx, 64, i - j, i, BIG_CHAR);
> +           }
> +       }
>      }
>
>    json_array_end (&json_ctx);
> --
> 2.34.1
>