![John Stultz](/assets/img/avatar_default.png)
Adds my nanosleep latency test from the timetest suite. This checks to make sure we don't see "unreasonable" latencies (> 40ms) when calling nanosleep. Cc: Shuah Khan <shuahkh@osg.samsung.com> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Richard Cochran <richardcochran@gmail.com> Signed-off-by: John Stultz <john.stultz@linaro.org> Tested-by: Prarit Bhargava <prarit@redhat.com> Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
191 lines
4.4 KiB
C
191 lines
4.4 KiB
C
/* Measure nanosleep timer latency
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* by: john stultz (john.stultz@linaro.org)
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* (C) Copyright Linaro 2013
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* Licensed under the GPLv2
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*
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* To build:
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* $ gcc nsleep-lat.c -o nsleep-lat -lrt
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <time.h>
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#include <sys/time.h>
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#include <sys/timex.h>
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#include <string.h>
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#include <signal.h>
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#ifdef KTEST
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#include "../kselftest.h"
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#else
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static inline int ksft_exit_pass(void)
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{
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exit(0);
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}
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static inline int ksft_exit_fail(void)
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{
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exit(1);
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}
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#endif
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#define NSEC_PER_SEC 1000000000ULL
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#define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
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#define CLOCK_REALTIME 0
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#define CLOCK_MONOTONIC 1
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#define CLOCK_PROCESS_CPUTIME_ID 2
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#define CLOCK_THREAD_CPUTIME_ID 3
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#define CLOCK_MONOTONIC_RAW 4
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#define CLOCK_REALTIME_COARSE 5
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#define CLOCK_MONOTONIC_COARSE 6
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#define CLOCK_BOOTTIME 7
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#define CLOCK_REALTIME_ALARM 8
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#define CLOCK_BOOTTIME_ALARM 9
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#define CLOCK_HWSPECIFIC 10
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#define CLOCK_TAI 11
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#define NR_CLOCKIDS 12
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#define UNSUPPORTED 0xf00f
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char *clockstring(int clockid)
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{
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switch (clockid) {
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case CLOCK_REALTIME:
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return "CLOCK_REALTIME";
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case CLOCK_MONOTONIC:
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return "CLOCK_MONOTONIC";
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case CLOCK_PROCESS_CPUTIME_ID:
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return "CLOCK_PROCESS_CPUTIME_ID";
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case CLOCK_THREAD_CPUTIME_ID:
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return "CLOCK_THREAD_CPUTIME_ID";
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case CLOCK_MONOTONIC_RAW:
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return "CLOCK_MONOTONIC_RAW";
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case CLOCK_REALTIME_COARSE:
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return "CLOCK_REALTIME_COARSE";
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case CLOCK_MONOTONIC_COARSE:
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return "CLOCK_MONOTONIC_COARSE";
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case CLOCK_BOOTTIME:
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return "CLOCK_BOOTTIME";
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case CLOCK_REALTIME_ALARM:
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return "CLOCK_REALTIME_ALARM";
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case CLOCK_BOOTTIME_ALARM:
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return "CLOCK_BOOTTIME_ALARM";
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case CLOCK_TAI:
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return "CLOCK_TAI";
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};
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return "UNKNOWN_CLOCKID";
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}
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struct timespec timespec_add(struct timespec ts, unsigned long long ns)
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{
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ts.tv_nsec += ns;
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while (ts.tv_nsec >= NSEC_PER_SEC) {
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ts.tv_nsec -= NSEC_PER_SEC;
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ts.tv_sec++;
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}
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return ts;
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}
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long long timespec_sub(struct timespec a, struct timespec b)
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{
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long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
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ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
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return ret;
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}
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int nanosleep_lat_test(int clockid, long long ns)
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{
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struct timespec start, end, target;
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long long latency = 0;
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int i, count;
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target.tv_sec = ns/NSEC_PER_SEC;
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target.tv_nsec = ns%NSEC_PER_SEC;
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if (clock_gettime(clockid, &start))
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return UNSUPPORTED;
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if (clock_nanosleep(clockid, 0, &target, NULL))
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return UNSUPPORTED;
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count = 10;
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/* First check relative latency */
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clock_gettime(clockid, &start);
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for (i = 0; i < count; i++)
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clock_nanosleep(clockid, 0, &target, NULL);
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clock_gettime(clockid, &end);
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if (((timespec_sub(start, end)/count)-ns) > UNRESONABLE_LATENCY) {
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printf("Large rel latency: %lld ns :", (timespec_sub(start, end)/count)-ns);
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return -1;
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}
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/* Next check absolute latency */
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for (i = 0; i < count; i++) {
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clock_gettime(clockid, &start);
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target = timespec_add(start, ns);
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clock_nanosleep(clockid, TIMER_ABSTIME, &target, NULL);
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clock_gettime(clockid, &end);
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latency += timespec_sub(target, end);
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}
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if (latency/count > UNRESONABLE_LATENCY) {
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printf("Large abs latency: %lld ns :", latency/count);
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return -1;
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}
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return 0;
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}
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int main(int argc, char **argv)
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{
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long long length;
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int clockid, ret;
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for (clockid = CLOCK_REALTIME; clockid < NR_CLOCKIDS; clockid++) {
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/* Skip cputime clockids since nanosleep won't increment cputime */
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if (clockid == CLOCK_PROCESS_CPUTIME_ID ||
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clockid == CLOCK_THREAD_CPUTIME_ID ||
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clockid == CLOCK_HWSPECIFIC)
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continue;
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printf("nsleep latency %-26s ", clockstring(clockid));
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length = 10;
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while (length <= (NSEC_PER_SEC * 10)) {
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ret = nanosleep_lat_test(clockid, length);
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if (ret)
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break;
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length *= 100;
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}
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if (ret == UNSUPPORTED) {
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printf("[UNSUPPORTED]\n");
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continue;
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}
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if (ret < 0) {
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printf("[FAILED]\n");
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return ksft_exit_fail();
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}
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printf("[OK]\n");
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}
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return ksft_exit_pass();
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}
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