benchtests: Add random memset benchmark

Add a new randomized memset test similar to bench-random-memcpy.  Instead of
repeating the same call to memset over and over again, it times a large number
of different inputs.  The distribution of memset length and alignment is based
on SPEC2017 (length up to 4096 and alignment up to 64).

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

2 files changed, 186 insertions, 0 deletions

diff --git a/benchtests/Makefile b/benchtests/Makefile
index 382fb7bae1..d228e9e68a 100644
--- a/benchtests/Makefile
+++ b/benchtests/Makefile
@@ -153,6 +153,7 @@ string-benchset := \
   memrchr \
   memset \
   memset-large \
+  memset-random \
   memset-zero \
   memset-zero-large \
   rawmemchr \
diff --git a/benchtests/bench-memset-random.c b/benchtests/bench-memset-random.c
new file mode 100644
index 0000000000..9c1eacbf81
--- /dev/null
+++ b/benchtests/bench-memset-random.c
@@ -0,0 +1,185 @@
+/* Measure memset 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 MIN_SIZE 32768
+#define MAX_SIZE (1024*1024)
+#define NUM_TESTS 16384
+
+#define MIN_PAGE_SIZE (MAX_SIZE + getpagesize())
+#define TEST_MAIN
+#define TEST_NAME "memset"
+#include "bench-string.h"
+#include <assert.h>
+#include "json-lib.h"
+
+typedef void *(*proto_t) (void *, int, size_t);
+
+IMPL (MEMSET, 1)
+
+typedef struct { uint32_t offset : 20, len : 12; } memset_test_t;
+static memset_test_t test_arr[NUM_TESTS];
+
+typedef struct { uint16_t size; uint16_t freq; } freq_data_t;
+typedef struct { uint8_t align; uint16_t freq; } align_data_t;
+
+#define SIZE_NUM 65536
+#define SIZE_MASK (SIZE_NUM-1)
+static uint8_t len_arr[SIZE_NUM];
+
+/* Frequency data for memset sizes up to 4096 bytes based on SPEC2017.  */
+static freq_data_t memset_len_freq[] =
+{
+{40,28817}, {32,15336}, { 16,3823}, {296,3545}, { 24,3454}, {  8,1412},
+{292,1202}, { 48, 927}, { 12, 613}, { 11, 539}, {284, 493}, {108, 414},
+{ 88, 380}, { 20, 295}, {312, 271}, { 72, 233}, {  2, 200}, {  4, 192},
+{ 15, 180}, { 14, 174}, { 13, 160}, { 56, 151}, { 36, 144}, { 64, 140},
+{4095,133}, { 10, 130}, {  9, 124}, {  3, 124}, { 28, 120}, {  0, 118},
+{288, 110}, {1152, 96}, {104,  90}, {  1,  86}, {832,  76}, {248,  74},
+{1024, 69}, {120,  64}, {512,  63}, {384,  60}, {  6,  59}, { 80,  54},
+{ 17,  50}, {  7,  49}, {520,  47}, {2048, 39}, {256,  37}, {864,  33},
+{1440, 28}, { 22,  27}, {2056, 24}, {260,  23}, { 68,  23}, {  5,  22},
+{ 18,  21}, {200,  18}, {2120, 18}, { 60,  17}, { 52,  16}, {336,  15},
+{ 44,  13}, {192,  13}, {160,  12}, {2064, 12}, {128,  12}, { 76,  11},
+{164,  11}, {152,  10}, {136,   9}, {488,   7}, { 96,   6}, {560,   6},
+{1016,  6}, {112,   5}, {232,   5}, {168,   5}, {952,   5}, {184,   5},
+{144,   4}, {252,   4}, { 84,   3}, {960,   3}, {3808,  3}, {244,   3},
+{280,   3}, {224,   3}, {156,   3}, {1088,  3}, {440,   3}, {216,   2},
+{304,   2}, { 23,   2}, { 25,   2}, { 26,   2}, {264,   2}, {328,   2},
+{1096,  2}, {240,   2}, {1104,  2}, {704,   2}, {1664,  2}, {360,   2},
+{808,   1}, {544,   1}, {236,   1}, {720,   1}, {368,   1}, {424,   1},
+{640,   1}, {1112,  1}, {552,   1}, {272,   1}, {776,   1}, {376,   1},
+{ 92,   1}, {536,   1}, {824,   1}, {496,   1}, {760,   1}, {792,   1},
+{504,   1}, {344,   1}, {1816,  1}, {880,   1}, {176,   1}, {320,   1},
+{352,   1}, {2008,  1}, {208,   1}, {408,   1}, {228,   1}, {2072,  1},
+{568,   1}, {220,   1}, {616,   1}, {600,   1}, {392,   1}, {696,   1},
+{2144,  1}, {1280,  1}, {2136,  1}, {632,   1}, {584,   1}, {456,   1},
+{472,   1}, {3440,  1}, {2088,  1}, {680,   1}, {2928,  1}, {212,   1},
+{648,   1}, {1752,  1}, {664,   1}, {3512,  1}, {1032,  1}, {528,   1},
+{4072,  1}, {204,   1}, {2880,  1}, {3392,  1}, {712,   1}, { 59,   1},
+{736,   1}, {592,   1}, {2520,  1}, {744,   1}, {196,   1}, {172,   1},
+{728,   1}, {2040,  1}, {1192,  1}, {3600,  1}, {0, 0}
+};
+
+#define ALIGN_NUM 1024
+#define ALIGN_MASK (ALIGN_NUM-1)
+static uint8_t align_arr[ALIGN_NUM];
+
+/* Alignment data for memset based on SPEC2017.  */
+static align_data_t memset_align_freq[] =
+{
+  {16, 338}, {8, 307}, {32, 148}, {64, 131}, {4, 72}, {1, 23}, {2, 5}, {0, 0}
+};
+
+static void
+init_memset_distribution (void)
+{
+  int i, j, freq, size, n;
+
+  for (n = i = 0; (freq = memset_len_freq[i].freq) != 0; i++)
+    for (j = 0, size = memset_len_freq[i].size; j < freq; j++)
+      len_arr[n++] = size;
+  assert (n == SIZE_NUM);
+
+  for (n = i = 0; (freq = memset_align_freq[i].freq) != 0; i++)
+    for (j = 0, size = memset_align_freq[i].align; j < freq; j++)
+      align_arr[n++] = size - 1;
+  assert (n == ALIGN_NUM);
+}
+
+static void
+do_one_test (json_ctx_t *json_ctx, impl_t *impl, size_t iters,
+	     memset_test_t *input, size_t n)
+{
+  timing_t start, stop, cur;
+
+  /* Avoid 'cold start' performance penalty.  */
+  for (int j = 0; j < n; j++)
+    CALL (impl, buf1 + input[j].offset, 0, input[j].len);
+
+  TIMING_NOW (start);
+  for (int i = 0; i < iters; ++i)
+    for (int j = 0; j < n; j++)
+      CALL (impl, buf1 + input[j].offset, 0, input[j].len);
+  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 max_size)
+{
+  int n;
+
+  /* Create a random set of memset inputs strings with the given length
+     and alignment distributions.  */
+  for (n = 0; n < NUM_TESTS; n++)
+    {
+      int align = align_arr[rand () & ALIGN_MASK];
+      int len = len_arr[rand () & SIZE_MASK];
+
+      test_arr[n].offset = (rand () & (max_size - 1)) & ~align;
+      test_arr[n].len = len;
+    }
+
+  json_element_object_begin (json_ctx);
+  json_attr_uint (json_ctx, "length", (double) max_size);
+  json_array_begin (json_ctx, "timings");
+
+  FOR_EACH_IMPL (impl, 0)
+    do_one_test (json_ctx, impl, INNER_LOOP_ITERS_MEDIUM * 2, test_arr, n);
+
+  json_array_end (json_ctx);
+  json_element_object_end (json_ctx);
+}
+
+int
+test_main (void)
+{
+  json_ctx_t json_ctx;
+
+  test_init ();
+  init_memset_distribution ();
+  memset (buf1, 1, MIN_PAGE_SIZE);
+
+  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");
+  for (int i = MIN_SIZE; i <= MAX_SIZE; i = i * 2)
+    do_test (&json_ctx, i);
+
+  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>