1 /* Measure nanosleep timer latency
2 * by: john stultz ([email protected])
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 <include/vdso/time64.h>
28 #include "../kselftest.h"
29
30 #define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
31
32 /* CLOCK_HWSPECIFIC == CLOCK_SGI_CYCLE (Deprecated) */
33 #define CLOCK_HWSPECIFIC 10
34
35 #define UNSUPPORTED 0xf00f
36
clockstring(int clockid)37 char *clockstring(int clockid)
38 {
39 switch (clockid) {
40 case CLOCK_REALTIME:
41 return "CLOCK_REALTIME";
42 case CLOCK_MONOTONIC:
43 return "CLOCK_MONOTONIC";
44 case CLOCK_PROCESS_CPUTIME_ID:
45 return "CLOCK_PROCESS_CPUTIME_ID";
46 case CLOCK_THREAD_CPUTIME_ID:
47 return "CLOCK_THREAD_CPUTIME_ID";
48 case CLOCK_MONOTONIC_RAW:
49 return "CLOCK_MONOTONIC_RAW";
50 case CLOCK_REALTIME_COARSE:
51 return "CLOCK_REALTIME_COARSE";
52 case CLOCK_MONOTONIC_COARSE:
53 return "CLOCK_MONOTONIC_COARSE";
54 case CLOCK_BOOTTIME:
55 return "CLOCK_BOOTTIME";
56 case CLOCK_REALTIME_ALARM:
57 return "CLOCK_REALTIME_ALARM";
58 case CLOCK_BOOTTIME_ALARM:
59 return "CLOCK_BOOTTIME_ALARM";
60 case CLOCK_TAI:
61 return "CLOCK_TAI";
62 };
63 return "UNKNOWN_CLOCKID";
64 }
65
timespec_add(struct timespec ts,unsigned long long ns)66 struct timespec timespec_add(struct timespec ts, unsigned long long ns)
67 {
68 ts.tv_nsec += ns;
69 while (ts.tv_nsec >= NSEC_PER_SEC) {
70 ts.tv_nsec -= NSEC_PER_SEC;
71 ts.tv_sec++;
72 }
73 return ts;
74 }
75
76
timespec_sub(struct timespec a,struct timespec b)77 long long timespec_sub(struct timespec a, struct timespec b)
78 {
79 long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
80
81 ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
82 return ret;
83 }
84
nanosleep_lat_test(int clockid,long long ns)85 int nanosleep_lat_test(int clockid, long long ns)
86 {
87 struct timespec start, end, target;
88 long long latency = 0;
89 int i, count;
90
91 target.tv_sec = ns/NSEC_PER_SEC;
92 target.tv_nsec = ns%NSEC_PER_SEC;
93
94 if (clock_gettime(clockid, &start))
95 return UNSUPPORTED;
96 if (clock_nanosleep(clockid, 0, &target, NULL))
97 return UNSUPPORTED;
98
99 count = 10;
100
101 /* First check relative latency */
102 clock_gettime(clockid, &start);
103 for (i = 0; i < count; i++)
104 clock_nanosleep(clockid, 0, &target, NULL);
105 clock_gettime(clockid, &end);
106
107 if (((timespec_sub(start, end)/count)-ns) > UNRESONABLE_LATENCY) {
108 ksft_print_msg("Large rel latency: %lld ns :", (timespec_sub(start, end)/count)-ns);
109 return -1;
110 }
111
112 /* Next check absolute latency */
113 for (i = 0; i < count; i++) {
114 clock_gettime(clockid, &start);
115 target = timespec_add(start, ns);
116 clock_nanosleep(clockid, TIMER_ABSTIME, &target, NULL);
117 clock_gettime(clockid, &end);
118 latency += timespec_sub(target, end);
119 }
120
121 if (latency/count > UNRESONABLE_LATENCY) {
122 ksft_print_msg("Large abs latency: %lld ns :", latency/count);
123 return -1;
124 }
125
126 return 0;
127 }
128
129 #define SKIPPED_CLOCK_COUNT 3
130
main(int argc,char ** argv)131 int main(int argc, char **argv)
132 {
133 long long length;
134 int clockid, ret;
135 int max_clocks = CLOCK_TAI + 1;
136
137 ksft_print_header();
138 ksft_set_plan(max_clocks - CLOCK_REALTIME - SKIPPED_CLOCK_COUNT);
139
140 for (clockid = CLOCK_REALTIME; clockid < max_clocks; clockid++) {
141
142 /* Skip cputime clockids since nanosleep won't increment cputime */
143 if (clockid == CLOCK_PROCESS_CPUTIME_ID ||
144 clockid == CLOCK_THREAD_CPUTIME_ID ||
145 clockid == CLOCK_HWSPECIFIC)
146 continue;
147
148 length = 10;
149 while (length <= (NSEC_PER_SEC * 10)) {
150 ret = nanosleep_lat_test(clockid, length);
151 if (ret)
152 break;
153 length *= 100;
154
155 }
156
157 if (ret == UNSUPPORTED) {
158 ksft_test_result_skip("%s\n", clockstring(clockid));
159 } else {
160 ksft_test_result(ret >= 0, "%s\n",
161 clockstring(clockid));
162 }
163 }
164
165 ksft_finished();
166 }
167