[3/4] bench-strncmp.c: Add workloads on page boundary

Add strncmp workloads on page boundary.
---
 benchtests/bench-strncmp.c | 117 +++++++++++++++++++++++++++++++++++++
 1 file changed, 117 insertions(+)

On 6/12/20 4:10 PM, H.J. Lu via Libc-alpha wrote:
> Add strncmp workloads on page boundary.

This benchmark need some work.

Please post v2.

> ---
>  benchtests/bench-strncmp.c | 117 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 117 insertions(+)
> 
> diff --git a/benchtests/bench-strncmp.c b/benchtests/bench-strncmp.c
> index 95a59c9465..065c7e7789 100644
> --- a/benchtests/bench-strncmp.c
> +++ b/benchtests/bench-strncmp.c
> @@ -27,6 +27,7 @@
>  
>  #ifdef WIDE
>  # define L(str) L##str
> +# define STRDUP wcsdup

OK.

>  # define SIMPLE_STRNCMP simple_wcsncmp
>  
>  /* Wcsncmp uses signed semantics for comparison, not unsigned.
> @@ -48,6 +49,7 @@ simple_wcsncmp (const CHAR *s1, const CHAR *s2, size_t n)
>  
>  #else
>  # define L(str) str
> +# define STRDUP strdup

OK.

>  # define SIMPLE_STRNCMP simple_strncmp
>  
>  /* Strncmp uses unsigned semantics for comparison.  */
> @@ -190,6 +192,118 @@ do_test (json_ctx_t *json_ctx, size_t align1, size_t align2, size_t len, size_t
>    json_element_object_end (json_ctx);
>  }
>  
> +static void
> +do_test_page_boundary_1 (json_ctx_t *json_ctx, CHAR *s1, CHAR *s2,

Rename to "do_one_test_page_boundary"

> +			 size_t align1, size_t align2, size_t len,
> +			 size_t n, int exp_result)
> +{
> +  json_element_object_begin (json_ctx);
> +  json_attr_uint (json_ctx, "strlen", (double) len);
> +  json_attr_uint (json_ctx, "len", (double) n);
> +  json_attr_uint (json_ctx, "align1", (double) align1);
> +  json_attr_uint (json_ctx, "align2", (double) align2);
> +  json_array_begin (json_ctx, "timings");
> +  FOR_EACH_IMPL (impl, 0)
> +    do_one_test (json_ctx, impl, s1, s2, n, exp_result);
> +  json_array_end (json_ctx);
> +  json_element_object_end (json_ctx);

OK.

> +}
> +


Add a comment:

/* To trigger bug 25933 we need a size that is equal to the
   vector length times 4. In the case of AVX2 for Intel we
   need 32 * 4. We make this test generic and run it for all
   architectures as additional boundary testing for such
   related algorithms.  */

> +static void
> +do_test_page_boundary (json_ctx_t *json_ctx)

OK.

> +{
> +  size_t size = 32 * 4;
> +  size_t len;
> +  CHAR *s1 = (CHAR *) (buf1 + (BUF1PAGES - 1) * page_size);
> +  CHAR *s2 = (CHAR *) (buf2 + (BUF1PAGES - 1) * page_size);
> +  int exp_result;
> +
> +  memset (s1, 'a', page_size);
> +  memset (s2, 'a', page_size);
> +
> +  s1[(page_size / CHARBYTES) - 1] = (CHAR) 0;
> +

Add comment:

/* Iterate over a size that is just below where we expect
   the bug to trigger up to the size we expect will trigger
   the bug e.g. [99-128].  Likewise iterate the start of
   two strings between 30 and 31 bytes away from the
   boundary to simulate alignment changes.  */

> +  for (size_t s = 99; s <= size; s++)
> +    for (size_t s1a = 31; s1a < 32; s1a++)

Please make s1a iterate over [30,32) like s2a.

> +      for (size_t s2a = 30; s2a < 32; s2a++)
> +	{
> +	  size_t align1 = (page_size / CHARBYTES - s) - s1a;
> +	  size_t align2 = (page_size / CHARBYTES - s) - s2a;
> +	  CHAR *s1p = s1 + align1;
> +	  CHAR *s2p = s2 + align2;
> +	  len = (page_size / CHARBYTES) - 1 - align1;
> +	  exp_result = SIMPLE_STRNCMP (s1p, s2p, s);
> +	  do_test_page_boundary_1 (json_ctx, s1p, s2p, align1, align2,
> +				   len, s, exp_result);
> +	}
> +}
> +
> +static void
> +do_page_test (json_ctx_t *json_ctx, size_t offset1, size_t offset2,

Rename to do_one_test_page()

> +	      CHAR *s2)
> +{
> +  CHAR *s1;
> +  int exp_result;
> +
> +  if (offset1 * CHARBYTES  >= page_size
> +      || offset2 * CHARBYTES >= page_size)
> +    return;

OK. Nothing bigger than a page size because we only have one page to work within.

> +
> +  s1 = (CHAR *) buf1;
> +  s1 += offset1;
> +  s2 += offset2;
> +
> +  size_t len = (page_size / CHARBYTES) - offset1;
> +
> +  exp_result= *s1;
> +
> +  json_element_object_begin (json_ctx);
> +  json_attr_uint (json_ctx, "strlen", (double) len);
> +  json_attr_uint (json_ctx, "len", (double) page_size);
> +  json_attr_uint (json_ctx, "align1", (double) offset1);
> +  json_attr_uint (json_ctx, "align2", (double) offset2);
> +  json_array_begin (json_ctx, "timings");
> +  {
> +    FOR_EACH_IMPL (impl, 0)
> +      do_one_test (json_ctx, impl, s1, s2, page_size, -exp_result);
> +  }
> +  json_array_end (json_ctx);
> +  json_element_object_end (json_ctx);
> +
> +  json_element_object_begin (json_ctx);
> +  json_attr_uint (json_ctx, "strlen", (double) len);
> +  json_attr_uint (json_ctx, "len", (double) page_size);
> +  json_attr_uint (json_ctx, "align1", (double) offset1);
> +  json_attr_uint (json_ctx, "align2", (double) offset2);
> +  json_array_begin (json_ctx, "timings");
> +  {
> +    FOR_EACH_IMPL (impl, 0)
> +      do_one_test (json_ctx, impl, s1, s2, page_size, exp_result);
> +  }
> +  json_array_end (json_ctx);
> +  json_element_object_end (json_ctx);
> +}

OK.

> +
> +static void
> +do_test_page (json_ctx_t *json_ctx)
> +{
> +  size_t i;
> +  CHAR *s1, *s2;
> +
> +  s1 = (CHAR *) buf1;
> +  for (i = 0; i < (page_size / CHARBYTES) - 1; i++)
> +    s1[i] = 23;

Add a comment for this magic fill number.

> +  s1[i] = 0;
> +
> +  s2 = STRDUP (s1);
> +
> +  for (i = 0; i < 64; ++i)

Add a comment for these magic numbers.

> +    do_page_test (json_ctx, (3988 / CHARBYTES) + i,
> +		  (2636 / CHARBYTES), s2);

Call do_one_test_page()

> +
> +  free (s2);
> +}
> +
>  int
>  test_main (void)
>  {
> @@ -267,6 +381,9 @@ test_main (void)
>        do_test_limit (&json_ctx, 0, 0, 15 - i, 16 - i, 255, -1);
>      }
>  
> +  do_test_page_boundary (&json_ctx);
> +  do_test_page (&json_ctx);

OK.

> +
>    json_array_end (&json_ctx);
>    json_attr_object_end (&json_ctx);
>    json_attr_object_end (&json_ctx);
>