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_alloc(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 	unsigned int old;
65 
66 	init_stats(&fb_time_stats);
67 	init_stats(&tb_time_stats);
68 
69 	for (set_bits = 1; set_bits <= num_bits; set_bits <<= 1) {
70 		bitmap_zero(to_test, num_bits);
71 		skip = num_bits / set_bits;
72 		for (i = 0; i < num_bits; i += skip)
73 			set_bit(i, to_test);
74 
75 		for (i = 0; i < outer_iterations; i++) {
76 			old = accumulator;
77 			gettimeofday(&start, NULL);
78 			for (j = 0; j < inner_iterations; j++) {
79 				for_each_set_bit(bit, to_test, num_bits)
80 					workload(bit);
81 			}
82 			gettimeofday(&end, NULL);
83 			assert(old + (inner_iterations * set_bits) == accumulator);
84 			timersub(&end, &start, &diff);
85 			runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
86 			update_stats(&fb_time_stats, runtime_us);
87 
88 			old = accumulator;
89 			gettimeofday(&start, NULL);
90 			for (j = 0; j < inner_iterations; j++) {
91 				for (bit = 0; bit < num_bits; bit++) {
92 					if (asm_test_bit(bit, to_test))
93 						workload(bit);
94 				}
95 			}
96 			gettimeofday(&end, NULL);
97 			assert(old + (inner_iterations * set_bits) == accumulator);
98 			timersub(&end, &start, &diff);
99 			runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
100 			update_stats(&tb_time_stats, runtime_us);
101 		}
102 
103 		printf("%d operations %d bits set of %d bits\n",
104 			inner_iterations, set_bits, num_bits);
105 		time_average = avg_stats(&fb_time_stats);
106 		time_stddev = stddev_stats(&fb_time_stats);
107 		printf("  Average for_each_set_bit took: %.3f usec (+- %.3f usec)\n",
108 			time_average, time_stddev);
109 		time_average = avg_stats(&tb_time_stats);
110 		time_stddev = stddev_stats(&tb_time_stats);
111 		printf("  Average test_bit loop took:    %.3f usec (+- %.3f usec)\n",
112 			time_average, time_stddev);
113 
114 		if (use_of_val == accumulator)  /* Try to avoid compiler tricks. */
115 			printf("\n");
116 	}
117 	bitmap_free(to_test);
118 	return 0;
119 }
120 
121 int bench_mem_find_bit(int argc, const char **argv)
122 {
123 	int err = 0, i;
124 
125 	argc = parse_options(argc, argv, options, bench_usage, 0);
126 	if (argc) {
127 		usage_with_options(bench_usage, options);
128 		exit(EXIT_FAILURE);
129 	}
130 
131 	for (i = 1; i <= 2048; i <<= 1)
132 		do_for_each_set_bit(i);
133 
134 	return err;
135 }
136