1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Benchmark find_next_bit and related bit operations.
4 *
5 * Copyright 2020 Google LLC.
6 */
7 #include <stdlib.h>
8 #include "bench.h"
9 #include "../util/stat.h"
10 #include <linux/bitmap.h>
11 #include <linux/bitops.h>
12 #include <linux/time64.h>
13 #include <subcmd/parse-options.h>
14
15 static unsigned int outer_iterations = 5;
16 static unsigned int inner_iterations = 100000;
17
18 static const struct option options[] = {
19 OPT_UINTEGER('i', "outer-iterations", &outer_iterations,
20 "Number of outer iterations used"),
21 OPT_UINTEGER('j', "inner-iterations", &inner_iterations,
22 "Number of inner iterations used"),
23 OPT_END()
24 };
25
26 static const char *const bench_usage[] = {
27 "perf bench mem find_bit <options>",
28 NULL
29 };
30
31 static unsigned int accumulator;
32 static unsigned int use_of_val;
33
34 static noinline void workload(int val)
35 {
36 use_of_val += val;
37 accumulator++;
38 }
39
40 #if (defined(__i386__) || defined(__x86_64__)) && defined(__GCC_ASM_FLAG_OUTPUTS__)
41 static bool asm_test_bit(long nr, const unsigned long *addr)
42 {
43 bool oldbit;
44
45 asm volatile("bt %2,%1"
46 : "=@ccc" (oldbit)
47 : "m" (*(unsigned long *)addr), "Ir" (nr) : "memory");
48
49 return oldbit;
50 }
51 #else
52 #define asm_test_bit test_bit
53 #endif
54
55 static int do_for_each_set_bit(unsigned int num_bits)
56 {
57 unsigned long *to_test = bitmap_zalloc(num_bits);
58 struct timeval start, end, diff;
59 u64 runtime_us;
60 struct stats fb_time_stats, tb_time_stats;
61 double time_average, time_stddev;
62 unsigned int bit, i, j;
63 unsigned int set_bits, skip;
64
65 init_stats(&fb_time_stats);
66 init_stats(&tb_time_stats);
67
68 for (set_bits = 1; set_bits <= num_bits; set_bits <<= 1) {
69 bitmap_zero(to_test, num_bits);
70 skip = num_bits / set_bits;
71 for (i = 0; i < num_bits; i += skip)
72 __set_bit(i, to_test);
73
74 for (i = 0; i < outer_iterations; i++) {
75 #ifndef NDEBUG
76 unsigned int old = accumulator;
77 #endif
78
79 gettimeofday(&start, NULL);
80 for (j = 0; j < inner_iterations; j++) {
81 for_each_set_bit(bit, to_test, num_bits)
82 workload(bit);
83 }
84 gettimeofday(&end, NULL);
85 assert(old + (inner_iterations * set_bits) == accumulator);
86 timersub(&end, &start, &diff);
87 runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
88 update_stats(&fb_time_stats, runtime_us);
89
90 #ifndef NDEBUG
91 old = accumulator;
92 #endif
93 gettimeofday(&start, NULL);
94 for (j = 0; j < inner_iterations; j++) {
95 for (bit = 0; bit < num_bits; bit++) {
96 if (asm_test_bit(bit, to_test))
97 workload(bit);
98 }
99 }
100 gettimeofday(&end, NULL);
101 assert(old + (inner_iterations * set_bits) == accumulator);
102 timersub(&end, &start, &diff);
103 runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
104 update_stats(&tb_time_stats, runtime_us);
105 }
106
107 printf("%d operations %d bits set of %d bits\n",
108 inner_iterations, set_bits, num_bits);
109 time_average = avg_stats(&fb_time_stats);
110 time_stddev = stddev_stats(&fb_time_stats);
111 printf(" Average for_each_set_bit took: %.3f usec (+- %.3f usec)\n",
112 time_average, time_stddev);
113 time_average = avg_stats(&tb_time_stats);
114 time_stddev = stddev_stats(&tb_time_stats);
115 printf(" Average test_bit loop took: %.3f usec (+- %.3f usec)\n",
116 time_average, time_stddev);
117
118 if (use_of_val == accumulator) /* Try to avoid compiler tricks. */
119 printf("\n");
120 }
121 bitmap_free(to_test);
122 return 0;
123 }
124
125 int bench_mem_find_bit(int argc, const char **argv)
126 {
127 int err = 0, i;
128
129 argc = parse_options(argc, argv, options, bench_usage, 0);
130 if (argc) {
131 usage_with_options(bench_usage, options);
132 exit(EXIT_FAILURE);
133 }
134
135 for (i = 1; i <= 2048; i <<= 1)
136 do_for_each_set_bit(i);
137
138 return err;
139 }
140
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