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/* Measure nanosleep timer latency
* by: john stultz (john.stultz@linaro.org)
* (C) Copyright Linaro 2013
* Licensed under the GPLv2
*
* To build:
* $ gcc nsleep-lat.c -o nsleep-lat -lrt
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <sys/time.h>
#include <sys/timex.h>
#include <string.h>
#include <signal.h>
#include "../kselftest.h"
#define NSEC_PER_SEC 1000000000ULL
#define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
#define CLOCK_REALTIME 0
#define CLOCK_MONOTONIC 1
#define CLOCK_PROCESS_CPUTIME_ID 2
#define CLOCK_THREAD_CPUTIME_ID 3
#define CLOCK_MONOTONIC_RAW 4
#define CLOCK_REALTIME_COARSE 5
#define CLOCK_MONOTONIC_COARSE 6
#define CLOCK_BOOTTIME 7
#define CLOCK_REALTIME_ALARM 8
#define CLOCK_BOOTTIME_ALARM 9
#define CLOCK_HWSPECIFIC 10
#define CLOCK_TAI 11
#define NR_CLOCKIDS 12
#define UNSUPPORTED 0xf00f
char *clockstring(int clockid)
{
switch (clockid) {
case CLOCK_REALTIME:
return "CLOCK_REALTIME";
case CLOCK_MONOTONIC:
return "CLOCK_MONOTONIC";
case CLOCK_PROCESS_CPUTIME_ID:
return "CLOCK_PROCESS_CPUTIME_ID";
case CLOCK_THREAD_CPUTIME_ID:
return "CLOCK_THREAD_CPUTIME_ID";
case CLOCK_MONOTONIC_RAW:
return "CLOCK_MONOTONIC_RAW";
case CLOCK_REALTIME_COARSE:
return "CLOCK_REALTIME_COARSE";
case CLOCK_MONOTONIC_COARSE:
return "CLOCK_MONOTONIC_COARSE";
case CLOCK_BOOTTIME:
return "CLOCK_BOOTTIME";
case CLOCK_REALTIME_ALARM:
return "CLOCK_REALTIME_ALARM";
case CLOCK_BOOTTIME_ALARM:
return "CLOCK_BOOTTIME_ALARM";
case CLOCK_TAI:
return "CLOCK_TAI";
};
return "UNKNOWN_CLOCKID";
}
struct timespec timespec_add(struct timespec ts, unsigned long long ns)
{
ts.tv_nsec += ns;
while (ts.tv_nsec >= NSEC_PER_SEC) {
ts.tv_nsec -= NSEC_PER_SEC;
ts.tv_sec++;
}
return ts;
}
long long timespec_sub(struct timespec a, struct timespec b)
{
long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
return ret;
}
int nanosleep_lat_test(int clockid, long long ns)
{
struct timespec start, end, target;
long long latency = 0;
int i, count;
target.tv_sec = ns/NSEC_PER_SEC;
target.tv_nsec = ns%NSEC_PER_SEC;
if (clock_gettime(clockid, &start))
return UNSUPPORTED;
if (clock_nanosleep(clockid, 0, &target, NULL))
return UNSUPPORTED;
count = 10;
/* First check relative latency */
clock_gettime(clockid, &start);
for (i = 0; i < count; i++)
clock_nanosleep(clockid, 0, &target, NULL);
clock_gettime(clockid, &end);
if (((timespec_sub(start, end)/count)-ns) > UNRESONABLE_LATENCY) {
printf("Large rel latency: %lld ns :", (timespec_sub(start, end)/count)-ns);
return -1;
}
/* Next check absolute latency */
for (i = 0; i < count; i++) {
clock_gettime(clockid, &start);
target = timespec_add(start, ns);
clock_nanosleep(clockid, TIMER_ABSTIME, &target, NULL);
clock_gettime(clockid, &end);
latency += timespec_sub(target, end);
}
if (latency/count > UNRESONABLE_LATENCY) {
printf("Large abs latency: %lld ns :", latency/count);
return -1;
}
return 0;
}
int main(int argc, char **argv)
{
long long length;
int clockid, ret;
for (clockid = CLOCK_REALTIME; clockid < NR_CLOCKIDS; clockid++) {
/* Skip cputime clockids since nanosleep won't increment cputime */
if (clockid == CLOCK_PROCESS_CPUTIME_ID ||
clockid == CLOCK_THREAD_CPUTIME_ID ||
clockid == CLOCK_HWSPECIFIC)
continue;
printf("nsleep latency %-26s ", clockstring(clockid));
fflush(stdout);
length = 10;
while (length <= (NSEC_PER_SEC * 10)) {
ret = nanosleep_lat_test(clockid, length);
if (ret)
break;
length *= 100;
}
if (ret == UNSUPPORTED) {
printf("[UNSUPPORTED]\n");
continue;
}
if (ret < 0) {
printf("[FAILED]\n");
return ksft_exit_fail();
}
printf("[OK]\n");
}
return ksft_exit_pass();
}
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