Re: [PATCH v2] Add random memcpy test

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

On Thu, Feb 9, 2017 at 11:30 AM, Wilco Dijkstra <Wilco.Dijkstra@arm.com> wrote:
> The 2nd version of this patch removes the made-up distribution and one based on a real
> trace instead:
>
> Add a new randomized memcpy test for copies up to 256 bytes.  The distribution of size and
> alignment is based on a trace of SPEC2006 (other traces could be added in the future).
> Instead of repeating the same copy over and over again like the existing tests, it times several
> thousand different copies to more accurately estimate the overhead of branch prediction due to
> the different sizes and alignments.
>
> ChangeLog:
> 2017-02-09  Wilco Dijkstra  <wdijkstr@arm.com>
>
>         * benchtests/Makefile (string-benchset): Add memcpy-random.
>         * benchtests/bench-memcpy-random.c: New file.
>
>
> diff --git a/benchtests/Makefile b/benchtests/Makefile
> index 81edf8a933ce7371ac60c118a4a46daee6391800..a96e9533b3b2d7223c2ce90a723b6a434ba1a1ea 100644
> --- a/benchtests/Makefile
> +++ b/benchtests/Makefile
> @@ -37,7 +37,7 @@ string-benchset := bcopy bzero memccpy memchr memcmp memcpy memmem memmove \
>                    strcat strchr strchrnul strcmp strcpy strcspn strlen \
>                    strncasecmp strncat strncmp strncpy strnlen strpbrk strrchr \
>                    strspn strstr strcpy_chk stpcpy_chk memrchr strsep strtok \
> -                  strcoll memcpy-large memmove-large memset-large
> +                  strcoll memcpy-large memcpy-random memmove-large memset-large
>
>  # Build and run locale-dependent benchmarks only if we're building natively.
>  ifeq (no,$(cross-compiling))
> diff --git a/benchtests/bench-memcpy-random.c b/benchtests/bench-memcpy-random.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..0e6955b292cde96d3100429e19138ba3d0114096
> --- /dev/null
> +++ b/benchtests/bench-memcpy-random.c
> @@ -0,0 +1,157 @@
> +/* Measure memcpy performance.
> +   Copyright (C) 2016-2017 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; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#define MIN_PAGE_SIZE 131072
> +#define TEST_MAIN
> +#define TEST_NAME "memcpy-random"
> +#include "bench-string.h"
> +#include <assert.h>
> +
> +IMPL (memcpy, 0)
> +
> +#define NUM_COPIES 4096
> +
> +typedef struct { uint16_t size; uint16_t freq; } freq_data_t;
> +typedef struct { uint8_t align; uint8_t freq; } align_data_t;
> +
> +#define SIZE_NUM 1024
> +#define SIZE_MASK (SIZE_NUM-1)
> +static uint8_t size_arr[SIZE_NUM];
> +
> +/* Frequency data for memcpy of less than 256 bytes based on SPEC2006.  */
> +static freq_data_t size_freq[] =
> +{
> +  {  8, 576}, {104,  94}, { 24,  78}, { 48,  58}, { 32,  48}, { 16,  46},
> +  {  1,  30}, { 96,  12}, { 72,  11}, {216,  11}, {192,   8}, { 12,   7},
> +  {144,   5}, {  2,   4}, { 64,   4}, {120,   4}, {  4,   3}, { 40,   2},
> +  {  7,   2}, {168,   2}, {160,   2}, {128,   1}, {  3,   1}, {  9,   1},
> +  {176,   1}, {240,   1}, { 11,   1}, {  0,   1}, {  5,   1}, {  6,   1},
> +  { 80,   1}, { 52,   1}, {152,   1}, { 10,   1}, { 56,   1}, { 51,   1},
> +  { 14,   1}, {208,   1}, {  0,   0}
> +};
> +
> +#define ALIGN_NUM 256
> +#define ALIGN_MASK (ALIGN_NUM-1)
> +static uint8_t src_align_arr[ALIGN_NUM];
> +static uint8_t dst_align_arr[ALIGN_NUM];
> +
> +/* Source alignment frequency for memcpy based on SPEC2006.  */
> +static align_data_t src_align_freq[] =
> +{
> +  {16, 144}, {8, 86}, {3, 23}, {1, 3}, {0, 0}
> +};
> +
> +/* Destination alignment frequency for memcpy based on SPEC2006.  */
> +static align_data_t dst_align_freq[] =
> +{
> +  {16, 197}, {8, 30}, {3, 23}, {1, 6}, {0, 0}
> +};
> +
> +typedef struct
> +{
> +  uint16_t src;
> +  uint16_t dst;
> +  uint16_t len;
> +} copy_t;
> +
> +static copy_t copy[NUM_COPIES];
> +
> +typedef char *(*proto_t) (char *, const char *, size_t);
> +
> +static void
> +init_copy_distribution (void)
> +{
> +  int i, j, freq, size, n;
> +
> +  for (n = i = 0; freq = size_freq[i].freq; i++)
> +    for (j = 0, size = size_freq[i].size; j < freq; j++)
> +      size_arr[n++] = size;
> +  assert (n == SIZE_NUM);
> +
> +  for (n = i = 0; freq = src_align_freq[i].freq; i++)
> +    for (j = 0, size = src_align_freq[i].align; j < freq; j++)
> +      src_align_arr[n++] = size - 1;
> +  assert (n == ALIGN_NUM);
> +
> +  for (n = i = 0; freq = dst_align_freq[i].freq; i++)
> +    for (j = 0, size = dst_align_freq[i].align; j < freq; j++)
> +      dst_align_arr[n++] = size - 1;
> +  assert (n == ALIGN_NUM);
> +}
> +
> +
> +static void
> +do_one_test (impl_t *impl, char *dst, char *src, copy_t *copy, size_t n)
> +{
> +  timing_t start, stop, cur;
> +  size_t iters = INNER_LOOP_ITERS * 20;
> +
> +  TIMING_NOW (start);
> +  for (int i = 0; i < iters; ++i)
> +    for (int j = 0; j < n; j++)
> +      CALL (impl, dst + copy[j].dst, src + copy[j].src, copy[j].len);
> +  TIMING_NOW (stop);
> +
> +  TIMING_DIFF (cur, start, stop);
> +
> +  TIMING_PRINT_MEAN ((double) cur, (double) iters);
> +}
> +
> +static void
> +do_test (size_t max_size)
> +{
> +  for (int i = 0; i < max_size; i++)
> +    buf1[i] = i * 3;
> +
> +  /* Create a random set of copies with the given size and alignment
> +     distributions.  */
> +  for (int i = 0; i < NUM_COPIES; i++)
> +    {
> +      copy[i].dst = (rand () & (max_size - 1)) | 1;
> +      copy[i].dst &= ~dst_align_arr[rand () & ALIGN_MASK];
> +      copy[i].src = (rand () & (max_size - 1)) | 3;
> +      copy[i].src &= ~src_align_arr[rand () & ALIGN_MASK];
> +      copy[i].len = size_arr[rand () & SIZE_MASK];
> +    }
> +
> +  printf ("Memory size %6zd:", max_size);
> +
> +  FOR_EACH_IMPL (impl, 0)
> +    do_one_test (impl, (char *) buf2, (char *) buf1, copy, NUM_COPIES);
> +
> +  putchar ('\n');
> +}
> +
> +int
> +test_main (void)
> +{
> +  test_init ();
> +  init_copy_distribution ();
> +
> +  printf ("%23s", "");
> +  FOR_EACH_IMPL (impl, 0)
> +    printf ("\t%s", impl->name);
> +  putchar ('\n');
> +
> +  for (int i = 4; i <= 64; i = i * 2)
> +    do_test (i * 1024);
> +
> +  return ret;
> +}
> +
> +#include <support/test-driver.c>
>

I like it.  But with GCC 6, I got

bench-memcpy-random.c: In function ‘init_copy_distribution’:
bench-memcpy-random.c:81:3: error: suggest parentheses around
assignment used as truth value [-Werror=parentheses]
   for (n = i = 0; freq = size_freq[i].freq; i++)
   ^~~
bench-memcpy-random.c:86:3: error: suggest parentheses around
assignment used as truth value [-Werror=parentheses]
   for (n = i = 0; freq = src_align_freq[i].freq; i++)
   ^~~
bench-memcpy-random.c:91:3: error: suggest parentheses around
assignment used as truth value [-Werror=parentheses]
   for (n = i = 0; freq = dst_align_freq[i].freq; i++)
   ^~~
cc1: all warnings being treated as errors


-- 
H.J.