Re: [PATCH v1 2/5] benchtests: Add additional cases to bench-memcpy.c and bench-memmove.c

["H.J. Lu" <hjl.tools@gmail.com>]

On Mon, Nov 01, 2021 at 12:49:49AM -0500, Noah Goldstein wrote:
> This commit adds more benchmarks for the common memcpy/memmove
> benchmarks. The most signifcant cases are the half page offsets. The
> current versions leaves dst and src near page aligned which leads to
> false 4k aliasing on x86_64. This can add noise due to false
> dependencies from one run to the next. As well, this seems like more
> of an edge case that common case so it shouldn't be the only thing
> ---
>  benchtests/bench-memcpy.c  | 49 +++++++++++++++++++++++++++++++++-----
>  benchtests/bench-memmove.c | 26 +++++++++++++++++---
>  2 files changed, 66 insertions(+), 9 deletions(-)
> 
> diff --git a/benchtests/bench-memcpy.c b/benchtests/bench-memcpy.c
> index d9236a2282..744bea26d3 100644
> --- a/benchtests/bench-memcpy.c
> +++ b/benchtests/bench-memcpy.c
> @@ -40,7 +40,10 @@ do_one_test (json_ctx_t *json_ctx, impl_t *impl, char *dst, const char *src,
>  {
>    size_t i, iters = INNER_LOOP_ITERS;
>    timing_t start, stop, cur;
> -
> +  for (i = 0; i < iters / 64; ++i)
> +    {
> +      CALL (impl, dst, src, len);
> +    }
>    TIMING_NOW (start);
>    for (i = 0; i < iters; ++i)
>      {
> @@ -60,11 +63,11 @@ do_test (json_ctx_t *json_ctx, size_t align1, size_t align2, size_t len,
>    size_t i, j;
>    char *s1, *s2;
>    size_t repeats;
> -  align1 &= 63;
> +  align1 &= (getpagesize () - 1);
>    if (align1 + len >= page_size)
>      return;
>  
> -  align2 &= 63;
> +  align2 &= (getpagesize () - 1);
>    if (align2 + len >= page_size)
>      return;
>  
> @@ -99,7 +102,7 @@ test_main (void)
>  {
>    json_ctx_t json_ctx;
>    size_t i;
> -
> +  size_t half_page = getpagesize () / 2;
>    test_init ();
>  
>    json_init (&json_ctx, 0, stdout);
> @@ -121,8 +124,15 @@ test_main (void)
>      {
>        do_test (&json_ctx, 0, 0, 1 << i, 1);
>        do_test (&json_ctx, i, 0, 1 << i, 1);
> +      do_test (&json_ctx, i + 32, 0, 1 << i, 1);
>        do_test (&json_ctx, 0, i, 1 << i, 1);
> +      do_test (&json_ctx, 0, i + 32, 1 << i, 1);
>        do_test (&json_ctx, i, i, 1 << i, 1);
> +      do_test (&json_ctx, i + 32, i + 32, 1 << i, 1);
> +      do_test (&json_ctx, half_page, 0, 1 << i, 1);
> +      do_test (&json_ctx, half_page + i, 0, 1 << i, 1);
> +      do_test (&json_ctx, half_page, i, 1 << i, 1);
> +      do_test (&json_ctx, half_page + i, i, 1 << i, 1);
>      }
>  
>    for (i = 0; i < 32; ++i)
> @@ -131,16 +141,26 @@ test_main (void)
>        do_test (&json_ctx, i, 0, i, 0);
>        do_test (&json_ctx, 0, i, i, 0);
>        do_test (&json_ctx, i, i, i, 0);
> +      do_test (&json_ctx, half_page, 0, i, 0);
> +      do_test (&json_ctx, half_page + i, 0, i, 0);
> +      do_test (&json_ctx, half_page, i, i, 0);
> +      do_test (&json_ctx, half_page + i, i, i, 0);
> +      do_test (&json_ctx, getpagesize () - 1, 0, i, 0);
> +      do_test (&json_ctx, 0, getpagesize () - 1, i, 0);
>      }
>  
>    for (i = 3; i < 32; ++i)
>      {
>        if ((i & (i - 1)) == 0)
> -	continue;
> +        continue;
>        do_test (&json_ctx, 0, 0, 16 * i, 1);
>        do_test (&json_ctx, i, 0, 16 * i, 1);
>        do_test (&json_ctx, 0, i, 16 * i, 1);
>        do_test (&json_ctx, i, i, 16 * i, 1);
> +      do_test (&json_ctx, half_page, 0, 16 * i, 1);
> +      do_test (&json_ctx, half_page + i, 0, 16 * i, 1);
> +      do_test (&json_ctx, half_page, i, 16 * i, 1);
> +      do_test (&json_ctx, half_page + i, i, 16 * i, 1);
>      }
>  
>    for (i = 32; i < 64; ++i)
> @@ -149,16 +169,33 @@ test_main (void)
>        do_test (&json_ctx, i, 0, 32 * i, 1);
>        do_test (&json_ctx, 0, i, 32 * i, 1);
>        do_test (&json_ctx, i, i, 32 * i, 1);
> +      do_test (&json_ctx, half_page, 0, 32 * i, 1);
> +      do_test (&json_ctx, half_page + i, 0, 32 * i, 1);
> +      do_test (&json_ctx, half_page, i, 32 * i, 1);
> +      do_test (&json_ctx, half_page + i, i, 32 * i, 1);
>      }
>  
>    do_test (&json_ctx, 0, 0, getpagesize (), 1);
>  
> -  for (i = 0; i <= 32; ++i)
> +  for (i = 0; i <= 48; ++i)
>      {
>        do_test (&json_ctx, 0, 0, 2048 + 64 * i, 1);
>        do_test (&json_ctx, i, 0, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, i + 32, 0, 2048 + 64 * i, 1);
>        do_test (&json_ctx, 0, i, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, 0, i + 32, 2048 + 64 * i, 1);
>        do_test (&json_ctx, i, i, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, i + 32, i + 32, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, half_page, 0, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, half_page + i, 0, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, half_page, i, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, half_page + i, i, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, i, 1, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, 1, i, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, i + 32, 1, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, 1, i + 32, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, half_page + i, 1, 2048 + 64 * i, 1);
> +      do_test (&json_ctx, half_page + 1, i, 2048 + 64 * i, 1);
>      }
>  
>    json_array_end (&json_ctx);
> diff --git a/benchtests/bench-memmove.c b/benchtests/bench-memmove.c
> index 6becbf4782..855f4d0649 100644
> --- a/benchtests/bench-memmove.c
> +++ b/benchtests/bench-memmove.c
> @@ -34,7 +34,10 @@ do_one_test (json_ctx_t *json_ctx, impl_t *impl, char *dst, char *src,
>  {
>    size_t i, iters = INNER_LOOP_ITERS;
>    timing_t start, stop, cur;
> -
> +  for (i = 0; i < iters / 64; ++i)
> +    {
> +      CALL (impl, dst, src, len);
> +    }
>    TIMING_NOW (start);
>    for (i = 0; i < iters; ++i)
>      {
> @@ -53,11 +56,11 @@ do_test (json_ctx_t *json_ctx, size_t align1, size_t align2, size_t len)
>    size_t i, j;
>    char *s1, *s2;
>  
> -  align1 &= 63;
> +  align1 &= (getpagesize () - 1);
>    if (align1 + len >= page_size)
>      return;
>  
> -  align2 &= 63;
> +  align2 &= (getpagesize () - 1);
>    if (align2 + len >= page_size)
>      return;
>  
> @@ -85,6 +88,7 @@ test_main (void)
>  {
>    json_ctx_t json_ctx;
>    size_t i;
> +  size_t half_page = getpagesize () / 2;
>  
>    test_init ();
>  
> @@ -138,6 +142,22 @@ test_main (void)
>        do_test (&json_ctx, i, i, 32 * i);
>      }
>  
> +  for (i = 0; i <= 48; ++i)
> +    {
> +      do_test (&json_ctx, 0, 0, 2048 + 64 * i);
> +      do_test (&json_ctx, i, 0, 2048 + 64 * i);
> +      do_test (&json_ctx, 0, i, 2048 + 64 * i);
> +      do_test (&json_ctx, i, i, 2048 + 64 * i);
> +      do_test (&json_ctx, half_page, 0, 2048 + 64 * i);
> +      do_test (&json_ctx, 0, half_page, 2048 + 64 * i);
> +      do_test (&json_ctx, half_page + i, 0, 2048 + 64 * i);
> +      do_test (&json_ctx, i, half_page, 2048 + 64 * i);
> +      do_test (&json_ctx, half_page, i, 2048 + 64 * i);
> +      do_test (&json_ctx, 0, half_page + i, 2048 + 64 * i);
> +      do_test (&json_ctx, half_page + i, i, 2048 + 64 * i);
> +      do_test (&json_ctx, i, half_page + i, 2048 + 64 * i);
> +    }
> +
>    json_array_end (&json_ctx);
>    json_attr_object_end (&json_ctx);
>    json_attr_object_end (&json_ctx);
> -- 
> 2.25.1
>

LGTM.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Thanks.

H.J.