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 #ifdef KTEST
28 #include "../kselftest.h"
29 #else
ksft_exit_pass(void)30 static inline int ksft_exit_pass(void)
31 {
32 exit(0);
33 }
ksft_exit_fail(void)34 static inline int ksft_exit_fail(void)
35 {
36 exit(1);
37 }
38 #endif
39
40 #define NSEC_PER_SEC 1000000000ULL
41
42 #define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
43
44
45 #define CLOCK_REALTIME 0
46 #define CLOCK_MONOTONIC 1
47 #define CLOCK_PROCESS_CPUTIME_ID 2
48 #define CLOCK_THREAD_CPUTIME_ID 3
49 #define CLOCK_MONOTONIC_RAW 4
50 #define CLOCK_REALTIME_COARSE 5
51 #define CLOCK_MONOTONIC_COARSE 6
52 #define CLOCK_BOOTTIME 7
53 #define CLOCK_REALTIME_ALARM 8
54 #define CLOCK_BOOTTIME_ALARM 9
55 #define CLOCK_HWSPECIFIC 10
56 #define CLOCK_TAI 11
57 #define NR_CLOCKIDS 12
58
59 #define UNSUPPORTED 0xf00f
60
clockstring(int clockid)61 char *clockstring(int clockid)
62 {
63 switch (clockid) {
64 case CLOCK_REALTIME:
65 return "CLOCK_REALTIME";
66 case CLOCK_MONOTONIC:
67 return "CLOCK_MONOTONIC";
68 case CLOCK_PROCESS_CPUTIME_ID:
69 return "CLOCK_PROCESS_CPUTIME_ID";
70 case CLOCK_THREAD_CPUTIME_ID:
71 return "CLOCK_THREAD_CPUTIME_ID";
72 case CLOCK_MONOTONIC_RAW:
73 return "CLOCK_MONOTONIC_RAW";
74 case CLOCK_REALTIME_COARSE:
75 return "CLOCK_REALTIME_COARSE";
76 case CLOCK_MONOTONIC_COARSE:
77 return "CLOCK_MONOTONIC_COARSE";
78 case CLOCK_BOOTTIME:
79 return "CLOCK_BOOTTIME";
80 case CLOCK_REALTIME_ALARM:
81 return "CLOCK_REALTIME_ALARM";
82 case CLOCK_BOOTTIME_ALARM:
83 return "CLOCK_BOOTTIME_ALARM";
84 case CLOCK_TAI:
85 return "CLOCK_TAI";
86 };
87 return "UNKNOWN_CLOCKID";
88 }
89
timespec_add(struct timespec ts,unsigned long long ns)90 struct timespec timespec_add(struct timespec ts, unsigned long long ns)
91 {
92 ts.tv_nsec += ns;
93 while (ts.tv_nsec >= NSEC_PER_SEC) {
94 ts.tv_nsec -= NSEC_PER_SEC;
95 ts.tv_sec++;
96 }
97 return ts;
98 }
99
100
timespec_sub(struct timespec a,struct timespec b)101 long long timespec_sub(struct timespec a, struct timespec b)
102 {
103 long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
104
105 ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
106 return ret;
107 }
108
nanosleep_lat_test(int clockid,long long ns)109 int nanosleep_lat_test(int clockid, long long ns)
110 {
111 struct timespec start, end, target;
112 long long latency = 0;
113 int i, count;
114
115 target.tv_sec = ns/NSEC_PER_SEC;
116 target.tv_nsec = ns%NSEC_PER_SEC;
117
118 if (clock_gettime(clockid, &start))
119 return UNSUPPORTED;
120 if (clock_nanosleep(clockid, 0, &target, NULL))
121 return UNSUPPORTED;
122
123 count = 10;
124
125 /* First check relative latency */
126 clock_gettime(clockid, &start);
127 for (i = 0; i < count; i++)
128 clock_nanosleep(clockid, 0, &target, NULL);
129 clock_gettime(clockid, &end);
130
131 if (((timespec_sub(start, end)/count)-ns) > UNRESONABLE_LATENCY) {
132 printf("Large rel latency: %lld ns :", (timespec_sub(start, end)/count)-ns);
133 return -1;
134 }
135
136 /* Next check absolute latency */
137 for (i = 0; i < count; i++) {
138 clock_gettime(clockid, &start);
139 target = timespec_add(start, ns);
140 clock_nanosleep(clockid, TIMER_ABSTIME, &target, NULL);
141 clock_gettime(clockid, &end);
142 latency += timespec_sub(target, end);
143 }
144
145 if (latency/count > UNRESONABLE_LATENCY) {
146 printf("Large abs latency: %lld ns :", latency/count);
147 return -1;
148 }
149
150 return 0;
151 }
152
153
154
main(int argc,char ** argv)155 int main(int argc, char **argv)
156 {
157 long long length;
158 int clockid, ret;
159
160 for (clockid = CLOCK_REALTIME; clockid < NR_CLOCKIDS; clockid++) {
161
162 /* Skip cputime clockids since nanosleep won't increment cputime */
163 if (clockid == CLOCK_PROCESS_CPUTIME_ID ||
164 clockid == CLOCK_THREAD_CPUTIME_ID ||
165 clockid == CLOCK_HWSPECIFIC)
166 continue;
167
168 printf("nsleep latency %-26s ", clockstring(clockid));
169
170 length = 10;
171 while (length <= (NSEC_PER_SEC * 10)) {
172 ret = nanosleep_lat_test(clockid, length);
173 if (ret)
174 break;
175 length *= 100;
176
177 }
178
179 if (ret == UNSUPPORTED) {
180 printf("[UNSUPPORTED]\n");
181 continue;
182 }
183 if (ret < 0) {
184 printf("[FAILED]\n");
185 return ksft_exit_fail();
186 }
187 printf("[OK]\n");
188 }
189 return ksft_exit_pass();
190 }
191