benchtests: Add random strlen benchmark

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.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

diff --git a/benchtests/Makefile b/benchtests/Makefile
index 5a07d1f91dd98b54dc7c8e728cc23bfe16708266..cccee62eb0b042d90132c922ec635ce06789733d 100644 (file)
--- a/benchtests/Makefile
+++ b/benchtests/Makefile
@@ -201,6 +201,7 @@ 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 (file)
index 0000000..becd09a
--- /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));
+  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>