[PATCH] benchtests: Add random strlen benchmark
Adhemerval Zanella Netto
adhemerval.zanella@linaro.org
Tue Mar 4 15:28:25 GMT 2025
On 20/02/25 12:13, Wilco Dijkstra wrote:
>
> ping
>
>
> Add a new randomized strlen test similar to bench-random-memcpy. Instead of repeating
> the same call to strlen over and over again, it times a large number of different
> strings. The distribution of the string length and alignment is based on SPEC2017.
>
> ---
>
> diff --git a/benchtests/Makefile b/benchtests/Makefile
> index d228e9e68af3d73129591f3d875d6be545182eac..6d746ad2d4de78470b1f7936c34affbd6edb254a 100644
> --- a/benchtests/Makefile
> +++ b/benchtests/Makefile
> @@ -171,6 +171,7 @@ string-benchset := \
> strcpy_chk \
> strcspn \
> strlen \
> + strlen-random \
> strncasecmp \
> strncat \
> strncmp \
> diff --git a/benchtests/bench-strlen-random.c b/benchtests/bench-strlen-random.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..becd09a2caff40262127b732aadd7d0e4374e9aa
> --- /dev/null
> +++ b/benchtests/bench-strlen-random.c
> @@ -0,0 +1,194 @@
> +/* Measure strlen performance.
> + Copyright (C) 2024 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
> + <https://www.gnu.org/licenses/>. */
> +
> +#define TEST_MAIN
> +#define TEST_NAME "strlen"
> +
> +#define NUM_TESTS 65536
> +#define MAX_ALIGN 32
> +#define MAX_STRLEN 128
> +#define MIN_PAGE_SIZE (2 * getpagesize())
> +
> +#include "bench-string.h"
> +#include <assert.h>
> +#include "json-lib.h"
> +
> +typedef size_t (*proto_t) (const CHAR *);
> +
> +size_t memchr_strlen (const CHAR *);
> +
> +IMPL (memchr_strlen, 0)
> +
> +size_t
> +memchr_strlen (const CHAR *p)
> +{
> + return (const CHAR *)MEMCHR (p, 0, PTRDIFF_MAX) - p;
> +}
> +
> +IMPL (STRLEN, 1)
> +
> +static uint32_t strlen_tests[NUM_TESTS];
> +
> +typedef struct { uint16_t size; uint16_t freq; } freq_data_t;
> +typedef struct { uint16_t align; uint16_t freq; } align_data_t;
> +
> +#define SIZE_NUM 65536
> +#define SIZE_MASK (SIZE_NUM-1)
> +static uint8_t strlen_len_arr[SIZE_NUM];
> +
> +/* Frequency data for strlen sizes up to 256 based on SPEC2017. */
> +static freq_data_t strlen_len_freq[] =
> +{
> + { 12,22671}, { 18,12834}, { 13, 9555}, { 6, 6348}, { 17, 6095}, { 11, 2115},
> + { 10, 1335}, { 7, 814}, { 2, 646}, { 9, 483}, { 8, 471}, { 16, 418},
> + { 4, 390}, { 1, 388}, { 5, 233}, { 3, 204}, { 0, 79}, { 14, 79},
> + { 15, 69}, { 26, 36}, { 22, 35}, { 31, 24}, { 32, 24}, { 19, 21},
> + { 25, 17}, { 28, 15}, { 21, 14}, { 33, 14}, { 20, 13}, { 24, 9},
> + { 29, 9}, { 30, 9}, { 23, 7}, { 34, 7}, { 27, 6}, { 44, 5},
> + { 42, 4}, { 45, 3}, { 47, 3}, { 40, 2}, { 41, 2}, { 43, 2},
> + { 58, 2}, { 78, 2}, { 36, 2}, { 48, 1}, { 52, 1}, { 60, 1},
> + { 64, 1}, { 56, 1}, { 76, 1}, { 68, 1}, { 80, 1}, { 84, 1},
> + { 72, 1}, { 86, 1}, { 35, 1}, { 39, 1}, { 50, 1}, { 38, 1},
> + { 37, 1}, { 46, 1}, { 98, 1}, {102, 1}, {128, 1}, { 51, 1},
> + {107, 1}, { 0, 0}
> +};
> +
> +#define ALIGN_NUM 1024
> +#define ALIGN_MASK (ALIGN_NUM-1)
> +static uint8_t strlen_align_arr[ALIGN_NUM];
> +
> +/* Alignment data for strlen based on SPEC2017. */
> +static align_data_t string_align_freq[] =
> +{
> + {8, 470}, {32, 427}, {16, 99}, {1, 19}, {2, 6}, {4, 3}, {0, 0}
> +};
> +
> +static void
> +init_strlen_distribution (void)
> +{
> + int i, j, freq, size, n;
> +
> + for (n = i = 0; (freq = strlen_len_freq[i].freq) != 0; i++)
> + for (j = 0, size = strlen_len_freq[i].size; j < freq; j++)
> + strlen_len_arr[n++] = size;
> + assert (n == SIZE_NUM);
> +
> + for (n = i = 0; (freq = string_align_freq[i].freq) != 0; i++)
> + for (j = 0, size = string_align_freq[i].align; j < freq; j++)
> + strlen_align_arr[n++] = size;
> + assert (n == ALIGN_NUM);
> +}
> +
> +static volatile size_t maskv = 0;
> +
> +static void
> +do_one_test (json_ctx_t *json_ctx, impl_t *impl, size_t iters,
> + uint32_t *input, size_t n)
> +{
> + timing_t start, stop, cur;
> + size_t res = 0;
> + size_t mask = maskv;
> +
> + /* Avoid 'cold start' performance penalty. */
> + for (int i = 0; i < 10; i++)
> + for (int j = 0; j < n; j++)
> + CALL (impl, (const char*)buf1 + input[j]);
> +
> + TIMING_NOW (start);
> + for (int i = 0; i < iters; ++i)
> + for (int j = 0; j < n; j++)
> + res = CALL (impl, (const char*)buf1 + input[j] + (res & mask));
Should we be worried that 65536 (n) * 2048 (iters) might overflow the
hp_timing_t here?
Otherwise, LGTM.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> + 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 n;
> + uint8_t *a = buf1;
> + uint16_t index[MAX_ALIGN];
> +
> + memset (a, 'x', MIN_PAGE_SIZE);
> +
> + /* Create indices for strings at all alignments. */
> + for (int i = 0; i < MAX_ALIGN; i++)
> + {
> + index[i] = i * (MAX_STRLEN + 1);
> + a[index[i] + MAX_STRLEN] = 0;
> + }
> +
> + /* Create a random set of strlen input strings using the string length
> + and alignment distributions. */
> + for (n = 0; n < NUM_TESTS; n++)
> + {
> + int align = strlen_align_arr[rand () & ALIGN_MASK];
> + int exp_len = strlen_len_arr[rand () & SIZE_MASK];
> +
> + strlen_tests[n] =
> + index[(align + exp_len) & (MAX_ALIGN - 1)] + MAX_STRLEN - exp_len;
> + assert ((strlen_tests[n] & (align - 1)) == 0);
> + assert (strlen ((char*) a + strlen_tests[n]) == exp_len);
> + }
> +
> + json_element_object_begin (json_ctx);
> + json_array_begin (json_ctx, "timings");
> +
> + FOR_EACH_IMPL (impl, 0)
> + do_one_test (json_ctx, impl, INNER_LOOP_ITERS_MEDIUM, strlen_tests, n);
> +
> + json_array_end (json_ctx);
> + json_element_object_end (json_ctx);
> +}
> +
> +int
> +test_main (void)
> +{
> +
> + json_ctx_t json_ctx;
> +
> + test_init ();
> + init_strlen_distribution ();
> +
> + 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", "random");
> +
> + 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");
> + do_test (&json_ctx);
> +
> + 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>
>
More information about the Libc-alpha
mailing list