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
clockstring(int clockid)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
timespec_add(struct timespec ts,unsigned long long ns)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
timespec_sub(struct timespec a,struct timespec b)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
nanosleep_lat_test(int clockid,long long ns)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
main(int argc,char ** argv)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 fflush(stdout);
159
160 length = 10;
161 while (length <= (NSEC_PER_SEC * 10)) {
162 ret = nanosleep_lat_test(clockid, length);
163 if (ret)
164 break;
165 length *= 100;
166
167 }
168
169 if (ret == UNSUPPORTED) {
170 printf("[UNSUPPORTED]\n");
171 continue;
172 }
173 if (ret < 0) {
174 printf("[FAILED]\n");
175 return ksft_exit_fail();
176 }
177 printf("[OK]\n");
178 }
179 return ksft_exit_pass();
180 }
181