summaryrefslogtreecommitdiffstats
path: root/tools/testing/selftests/powerpc/benchmarks/null_syscall.c
blob: 9836838a529f68681b3090ba6f9ddddcc853d15f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Test null syscall performance
 *
 * Copyright (C) 2009-2015 Anton Blanchard, IBM
 */

#define NR_LOOPS 10000000

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/syscall.h>
#include <signal.h>

static volatile int soak_done;
unsigned long long clock_frequency;
unsigned long long timebase_frequency;
double timebase_multiplier;

static inline unsigned long mftb(void)
{
	unsigned long low;

	asm volatile("mftb %0" : "=r" (low));

	return low;
}

static void sigalrm_handler(int unused)
{
	soak_done = 1;
}

/*
 * Use a timer instead of busy looping on clock_gettime() so we don't
 * pollute profiles with glibc and VDSO hits.
 */
static void cpu_soak_usecs(unsigned long usecs)
{
	struct itimerval val;

	memset(&val, 0, sizeof(val));
	val.it_value.tv_usec = usecs;

	signal(SIGALRM, sigalrm_handler);
	setitimer(ITIMER_REAL, &val, NULL);

	while (1) {
		if (soak_done)
			break;
	}

	signal(SIGALRM, SIG_DFL);
}

/*
 * This only works with recent kernels where cpufreq modifies
 * /proc/cpuinfo dynamically.
 */
static void get_proc_frequency(void)
{
	FILE *f;
	char line[128];
	char *p, *end;
	unsigned long v;
	double d;
	char *override;

	/* Try to get out of low power/low frequency mode */
	cpu_soak_usecs(0.25 * 1000000);

	f = fopen("/proc/cpuinfo", "r");
	if (f == NULL)
		return;

	timebase_frequency = 0;

	while (fgets(line, sizeof(line), f) != NULL) {
		if (strncmp(line, "timebase", 8) == 0) {
			p = strchr(line, ':');
			if (p != NULL) {
				v = strtoull(p + 1, &end, 0);
				if (end != p + 1)
					timebase_frequency = v;
			}
		}

		if (((strncmp(line, "clock", 5) == 0) ||
		     (strncmp(line, "cpu MHz", 7) == 0))) {
			p = strchr(line, ':');
			if (p != NULL) {
				d = strtod(p + 1, &end);
				if (end != p + 1) {
					/* Find fastest clock frequency */
					if ((d * 1000000ULL) > clock_frequency)
						clock_frequency = d * 1000000ULL;
				}
			}
		}
	}

	fclose(f);

	override = getenv("FREQUENCY");
	if (override)
		clock_frequency = strtoull(override, NULL, 10);

	if (timebase_frequency)
		timebase_multiplier = (double)clock_frequency
					/ timebase_frequency;
	else
		timebase_multiplier = 1;
}

static void do_null_syscall(unsigned long nr)
{
	unsigned long i;

	for (i = 0; i < nr; i++)
		syscall(__NR_gettid);
}

#define TIME(A, STR) \

int main(void)
{
	unsigned long tb_start, tb_now;
	struct timespec tv_start, tv_now;
	unsigned long long elapsed_ns, elapsed_tb;

	get_proc_frequency();

	clock_gettime(CLOCK_MONOTONIC, &tv_start);
	tb_start = mftb();

	do_null_syscall(NR_LOOPS);

	clock_gettime(CLOCK_MONOTONIC, &tv_now);
	tb_now = mftb();

	elapsed_ns = (tv_now.tv_sec - tv_start.tv_sec) * 1000000000ULL +
			(tv_now.tv_nsec - tv_start.tv_nsec);
	elapsed_tb = tb_now - tb_start;

	printf("%10.2f ns %10.2f cycles\n", (float)elapsed_ns / NR_LOOPS,
			(float)elapsed_tb * timebase_multiplier / NR_LOOPS);

	return 0;
}