kselftests: timers: Add test for frequency step
This test checks the response of the system clock to frequency steps made with adjtimex(). The frequency error and stability of the CLOCK_MONOTONIC clock relative to the CLOCK_MONOTONIC_RAW clock is measured in two intervals following the step. The test fails if values from the second interval exceed specified limits. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Miroslav Lichvar <mlichvar@redhat.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Stephen Boyd <stephen.boyd@linaro.org> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com> Signed-off-by: John Stultz <john.stultz@linaro.org>
This commit is contained in:
Miroslav Lichvar
John Stultz
parent
7a5de55122
commit
767392565a
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@ -1,6 +1,6 @@
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BUILD_FLAGS = -DKTEST
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CFLAGS += -O3 -Wl,-no-as-needed -Wall $(BUILD_FLAGS)
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LDFLAGS += -lrt -lpthread
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LDFLAGS += -lrt -lpthread -lm
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# these are all "safe" tests that don't modify
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# system time or require escalated privileges
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@ -8,7 +8,7 @@ TEST_GEN_PROGS = posix_timers nanosleep nsleep-lat set-timer-lat mqueue-lat \
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inconsistency-check raw_skew threadtest rtctest
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TEST_GEN_PROGS_EXTENDED = alarmtimer-suspend valid-adjtimex adjtick change_skew \
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skew_consistency clocksource-switch leap-a-day \
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skew_consistency clocksource-switch freq-step leap-a-day \
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leapcrash set-tai set-2038 set-tz
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@ -24,6 +24,7 @@ run_destructive_tests: run_tests
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./change_skew
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./skew_consistency
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./clocksource-switch
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./freq-step
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./leap-a-day -s -i 10
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./leapcrash
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./set-tz
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@ -0,0 +1,268 @@
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/*
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* This test checks the response of the system clock to frequency
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* steps made with adjtimex(). The frequency error and stability of
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* the CLOCK_MONOTONIC clock relative to the CLOCK_MONOTONIC_RAW clock
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* is measured in two intervals following the step. The test fails if
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* values from the second interval exceed specified limits.
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*
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* Copyright (C) Miroslav Lichvar <mlichvar@redhat.com> 2017
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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 version 2 of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#include <math.h>
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#include <stdio.h>
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#include <sys/timex.h>
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#include <time.h>
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#include <unistd.h>
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#include "../kselftest.h"
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#define SAMPLES 100
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#define SAMPLE_READINGS 10
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#define MEAN_SAMPLE_INTERVAL 0.1
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#define STEP_INTERVAL 1.0
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#define MAX_PRECISION 100e-9
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#define MAX_FREQ_ERROR 10e-6
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#define MAX_STDDEV 1000e-9
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struct sample {
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double offset;
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double time;
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};
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static time_t mono_raw_base;
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static time_t mono_base;
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static long user_hz;
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static double precision;
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static double mono_freq_offset;
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static double diff_timespec(struct timespec *ts1, struct timespec *ts2)
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{
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return ts1->tv_sec - ts2->tv_sec + (ts1->tv_nsec - ts2->tv_nsec) / 1e9;
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}
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static double get_sample(struct sample *sample)
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{
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double delay, mindelay = 0.0;
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struct timespec ts1, ts2, ts3;
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int i;
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for (i = 0; i < SAMPLE_READINGS; i++) {
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clock_gettime(CLOCK_MONOTONIC_RAW, &ts1);
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clock_gettime(CLOCK_MONOTONIC, &ts2);
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clock_gettime(CLOCK_MONOTONIC_RAW, &ts3);
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ts1.tv_sec -= mono_raw_base;
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ts2.tv_sec -= mono_base;
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ts3.tv_sec -= mono_raw_base;
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delay = diff_timespec(&ts3, &ts1);
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if (delay <= 1e-9) {
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i--;
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continue;
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}
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if (!i || delay < mindelay) {
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sample->offset = diff_timespec(&ts2, &ts1);
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sample->offset -= delay / 2.0;
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sample->time = ts1.tv_sec + ts1.tv_nsec / 1e9;
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mindelay = delay;
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}
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}
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return mindelay;
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}
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static void reset_ntp_error(void)
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{
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struct timex txc;
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txc.modes = ADJ_SETOFFSET;
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txc.time.tv_sec = 0;
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txc.time.tv_usec = 0;
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if (adjtimex(&txc) < 0) {
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perror("[FAIL] adjtimex");
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ksft_exit_fail();
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}
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}
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static void set_frequency(double freq)
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{
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struct timex txc;
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int tick_offset;
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tick_offset = 1e6 * freq / user_hz;
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txc.modes = ADJ_TICK | ADJ_FREQUENCY;
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txc.tick = 1000000 / user_hz + tick_offset;
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txc.freq = (1e6 * freq - user_hz * tick_offset) * (1 << 16);
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if (adjtimex(&txc) < 0) {
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perror("[FAIL] adjtimex");
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ksft_exit_fail();
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}
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}
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static void regress(struct sample *samples, int n, double *intercept,
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double *slope, double *r_stddev, double *r_max)
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{
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double x, y, r, x_sum, y_sum, xy_sum, x2_sum, r2_sum;
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int i;
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x_sum = 0.0, y_sum = 0.0, xy_sum = 0.0, x2_sum = 0.0;
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for (i = 0; i < n; i++) {
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x = samples[i].time;
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y = samples[i].offset;
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x_sum += x;
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y_sum += y;
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xy_sum += x * y;
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x2_sum += x * x;
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}
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*slope = (xy_sum - x_sum * y_sum / n) / (x2_sum - x_sum * x_sum / n);
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*intercept = (y_sum - *slope * x_sum) / n;
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*r_max = 0.0, r2_sum = 0.0;
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for (i = 0; i < n; i++) {
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x = samples[i].time;
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y = samples[i].offset;
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r = fabs(x * *slope + *intercept - y);
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if (*r_max < r)
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*r_max = r;
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r2_sum += r * r;
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}
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*r_stddev = sqrt(r2_sum / n);
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}
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static int run_test(int calibration, double freq_base, double freq_step)
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{
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struct sample samples[SAMPLES];
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double intercept, slope, stddev1, max1, stddev2, max2;
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double freq_error1, freq_error2;
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int i;
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set_frequency(freq_base);
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for (i = 0; i < 10; i++)
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usleep(1e6 * MEAN_SAMPLE_INTERVAL / 10);
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reset_ntp_error();
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set_frequency(freq_base + freq_step);
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for (i = 0; i < 10; i++)
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usleep(rand() % 2000000 * STEP_INTERVAL / 10);
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set_frequency(freq_base);
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for (i = 0; i < SAMPLES; i++) {
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usleep(rand() % 2000000 * MEAN_SAMPLE_INTERVAL);
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get_sample(&samples[i]);
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}
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if (calibration) {
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regress(samples, SAMPLES, &intercept, &slope, &stddev1, &max1);
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mono_freq_offset = slope;
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printf("CLOCK_MONOTONIC_RAW frequency offset: %11.3f ppm\n",
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1e6 * mono_freq_offset);
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return 0;
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}
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regress(samples, SAMPLES / 2, &intercept, &slope, &stddev1, &max1);
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freq_error1 = slope * (1.0 - mono_freq_offset) - mono_freq_offset -
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freq_base;
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regress(samples + SAMPLES / 2, SAMPLES / 2, &intercept, &slope,
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&stddev2, &max2);
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freq_error2 = slope * (1.0 - mono_freq_offset) - mono_freq_offset -
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freq_base;
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printf("%6.0f %+10.3f %6.0f %7.0f %+10.3f %6.0f %7.0f\t",
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1e6 * freq_step,
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1e6 * freq_error1, 1e9 * stddev1, 1e9 * max1,
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1e6 * freq_error2, 1e9 * stddev2, 1e9 * max2);
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if (fabs(freq_error2) > MAX_FREQ_ERROR || stddev2 > MAX_STDDEV) {
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printf("[FAIL]\n");
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return 1;
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}
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printf("[OK]\n");
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return 0;
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}
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static void init_test(void)
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{
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struct timespec ts;
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struct sample sample;
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if (clock_gettime(CLOCK_MONOTONIC_RAW, &ts)) {
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perror("[FAIL] clock_gettime(CLOCK_MONOTONIC_RAW)");
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ksft_exit_fail();
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}
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mono_raw_base = ts.tv_sec;
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if (clock_gettime(CLOCK_MONOTONIC, &ts)) {
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perror("[FAIL] clock_gettime(CLOCK_MONOTONIC)");
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ksft_exit_fail();
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}
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mono_base = ts.tv_sec;
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user_hz = sysconf(_SC_CLK_TCK);
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precision = get_sample(&sample) / 2.0;
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printf("CLOCK_MONOTONIC_RAW+CLOCK_MONOTONIC precision: %.0f ns\t\t",
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1e9 * precision);
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if (precision > MAX_PRECISION) {
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printf("[SKIP]\n");
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ksft_exit_skip();
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}
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printf("[OK]\n");
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srand(ts.tv_sec ^ ts.tv_nsec);
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run_test(1, 0.0, 0.0);
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}
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int main(int argc, char **argv)
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{
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double freq_base, freq_step;
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int i, j, fails = 0;
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init_test();
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printf("Checking response to frequency step:\n");
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printf(" Step 1st interval 2nd interval\n");
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printf(" Freq Dev Max Freq Dev Max\n");
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for (i = 2; i >= 0; i--) {
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for (j = 0; j < 5; j++) {
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freq_base = (rand() % (1 << 24) - (1 << 23)) / 65536e6;
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freq_step = 10e-6 * (1 << (6 * i));
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fails += run_test(0, freq_base, freq_step);
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}
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}
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set_frequency(0.0);
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if (fails)
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ksft_exit_fail();
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ksft_exit_pass();
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}
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