1 /* Measure nanosleep timer latency
2  *              by: john stultz (john.stultz@linaro.org)
3  *		(C) Copyright Linaro 2013
4  *              Licensed under the GPLv2
5  *
6  *  To build:
7  *	$ gcc nsleep-lat.c -o nsleep-lat -lrt
8  *
9  *   This program is free software: you can redistribute it and/or modify
10  *   it under the terms of the GNU General Public License as published by
11  *   the Free Software Foundation, either version 2 of the License, or
12  *   (at your option) any later version.
13  *
14  *   This program is distributed in the hope that it will be useful,
15  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
16  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17  *   GNU General Public License for more details.
18  */
19 
20 #include <stdio.h>
21 #include <stdlib.h>
22 #include <time.h>
23 #include <sys/time.h>
24 #include <sys/timex.h>
25 #include <string.h>
26 #include <signal.h>
27 #include "../kselftest.h"
28 
29 #define NSEC_PER_SEC 1000000000ULL
30 
31 #define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
32 
33 
34 #define CLOCK_REALTIME			0
35 #define CLOCK_MONOTONIC			1
36 #define CLOCK_PROCESS_CPUTIME_ID	2
37 #define CLOCK_THREAD_CPUTIME_ID		3
38 #define CLOCK_MONOTONIC_RAW		4
39 #define CLOCK_REALTIME_COARSE		5
40 #define CLOCK_MONOTONIC_COARSE		6
41 #define CLOCK_BOOTTIME			7
42 #define CLOCK_REALTIME_ALARM		8
43 #define CLOCK_BOOTTIME_ALARM		9
44 #define CLOCK_HWSPECIFIC		10
45 #define CLOCK_TAI			11
46 #define NR_CLOCKIDS			12
47 
48 #define UNSUPPORTED 0xf00f
49 
50 char *clockstring(int clockid)
51 {
52 	switch (clockid) {
53 	case CLOCK_REALTIME:
54 		return "CLOCK_REALTIME";
55 	case CLOCK_MONOTONIC:
56 		return "CLOCK_MONOTONIC";
57 	case CLOCK_PROCESS_CPUTIME_ID:
58 		return "CLOCK_PROCESS_CPUTIME_ID";
59 	case CLOCK_THREAD_CPUTIME_ID:
60 		return "CLOCK_THREAD_CPUTIME_ID";
61 	case CLOCK_MONOTONIC_RAW:
62 		return "CLOCK_MONOTONIC_RAW";
63 	case CLOCK_REALTIME_COARSE:
64 		return "CLOCK_REALTIME_COARSE";
65 	case CLOCK_MONOTONIC_COARSE:
66 		return "CLOCK_MONOTONIC_COARSE";
67 	case CLOCK_BOOTTIME:
68 		return "CLOCK_BOOTTIME";
69 	case CLOCK_REALTIME_ALARM:
70 		return "CLOCK_REALTIME_ALARM";
71 	case CLOCK_BOOTTIME_ALARM:
72 		return "CLOCK_BOOTTIME_ALARM";
73 	case CLOCK_TAI:
74 		return "CLOCK_TAI";
75 	};
76 	return "UNKNOWN_CLOCKID";
77 }
78 
79 struct timespec timespec_add(struct timespec ts, unsigned long long ns)
80 {
81 	ts.tv_nsec += ns;
82 	while (ts.tv_nsec >= NSEC_PER_SEC) {
83 		ts.tv_nsec -= NSEC_PER_SEC;
84 		ts.tv_sec++;
85 	}
86 	return ts;
87 }
88 
89 
90 long long timespec_sub(struct timespec a, struct timespec b)
91 {
92 	long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
93 
94 	ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
95 	return ret;
96 }
97 
98 int nanosleep_lat_test(int clockid, long long ns)
99 {
100 	struct timespec start, end, target;
101 	long long latency = 0;
102 	int i, count;
103 
104 	target.tv_sec = ns/NSEC_PER_SEC;
105 	target.tv_nsec = ns%NSEC_PER_SEC;
106 
107 	if (clock_gettime(clockid, &start))
108 		return UNSUPPORTED;
109 	if (clock_nanosleep(clockid, 0, &target, NULL))
110 		return UNSUPPORTED;
111 
112 	count = 10;
113 
114 	/* First check relative latency */
115 	clock_gettime(clockid, &start);
116 	for (i = 0; i < count; i++)
117 		clock_nanosleep(clockid, 0, &target, NULL);
118 	clock_gettime(clockid, &end);
119 
120 	if (((timespec_sub(start, end)/count)-ns) > UNRESONABLE_LATENCY) {
121 		printf("Large rel latency: %lld ns :", (timespec_sub(start, end)/count)-ns);
122 		return -1;
123 	}
124 
125 	/* Next check absolute latency */
126 	for (i = 0; i < count; i++) {
127 		clock_gettime(clockid, &start);
128 		target = timespec_add(start, ns);
129 		clock_nanosleep(clockid, TIMER_ABSTIME, &target, NULL);
130 		clock_gettime(clockid, &end);
131 		latency += timespec_sub(target, end);
132 	}
133 
134 	if (latency/count > UNRESONABLE_LATENCY) {
135 		printf("Large abs latency: %lld ns :", latency/count);
136 		return -1;
137 	}
138 
139 	return 0;
140 }
141 
142 
143 
144 int main(int argc, char **argv)
145 {
146 	long long length;
147 	int clockid, ret;
148 
149 	for (clockid = CLOCK_REALTIME; clockid < NR_CLOCKIDS; clockid++) {
150 
151 		/* Skip cputime clockids since nanosleep won't increment cputime */
152 		if (clockid == CLOCK_PROCESS_CPUTIME_ID ||
153 				clockid == CLOCK_THREAD_CPUTIME_ID ||
154 				clockid == CLOCK_HWSPECIFIC)
155 			continue;
156 
157 		printf("nsleep latency %-26s ", clockstring(clockid));
158 
159 		length = 10;
160 		while (length <= (NSEC_PER_SEC * 10)) {
161 			ret = nanosleep_lat_test(clockid, length);
162 			if (ret)
163 				break;
164 			length *= 100;
165 
166 		}
167 
168 		if (ret == UNSUPPORTED) {
169 			printf("[UNSUPPORTED]\n");
170 			continue;
171 		}
172 		if (ret < 0) {
173 			printf("[FAILED]\n");
174 			return ksft_exit_fail();
175 		}
176 		printf("[OK]\n");
177 	}
178 	return ksft_exit_pass();
179 }
180