diff options
Diffstat (limited to 'src/kernel/tests/lib/tst_timer_test.c')
| -rw-r--r-- | src/kernel/tests/lib/tst_timer_test.c | 472 |
1 files changed, 472 insertions, 0 deletions
diff --git a/src/kernel/tests/lib/tst_timer_test.c b/src/kernel/tests/lib/tst_timer_test.c new file mode 100644 index 0000000..196c512 --- /dev/null +++ b/src/kernel/tests/lib/tst_timer_test.c @@ -0,0 +1,472 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (c) 2017 Cyril Hrubis <chrubis@suse.cz> + */ + +#include <sys/prctl.h> +#include <stdlib.h> +#include <stdio.h> +#include <limits.h> +#include <string.h> + +#define TST_NO_DEFAULT_MAIN +#include "tst_test.h" +#include "tst_clocks.h" +#include "tst_timer_test.h" + +#define MAX_SAMPLES 500 + +static const char *scall; +static void (*setup)(void); +static void (*cleanup)(void); +static int (*sample)(int clk_id, long long usec); +static struct tst_test *test; + +static long long *samples; +static unsigned int cur_sample; +static unsigned int monotonic_resolution; +static unsigned int timerslack; +static int virt_env; + +static char *print_frequency_plot; +static char *file_name; +static char *str_sleep_time; +static char *str_sample_cnt; +static int sleep_time = -1; +static int sample_cnt; + +static void print_line(char c, int len) +{ + while (len-- > 0) + fputc(c, stderr); +} + +static unsigned int ceilu(float f) +{ + if (f - (int)f > 0) + return (unsigned int)f + 1; + + return (unsigned int)f; +} + +static unsigned int flooru(float f) +{ + return (unsigned int)f; +} + +static float bucket_len(unsigned int bucket, unsigned int max_bucket, + unsigned int cols) +{ + return 1.00 * bucket * cols / max_bucket; +} + +static const char *table_heading = " Time: us "; + +/* + * Line Header: '10023 | ' + */ +static unsigned int header_len(long long max_sample) +{ + unsigned int l = 1; + + while (max_sample/=10) + l++; + + return MAX(strlen(table_heading) + 2, l + 3); +} + +static void frequency_plot(void) +{ + unsigned int cols = 80; + unsigned int rows = 20; + unsigned int i, buckets[rows]; + long long max_sample = samples[0]; + long long min_sample = samples[cur_sample-1]; + unsigned int line_header_len = header_len(max_sample); + unsigned int plot_line_len = cols - line_header_len; + unsigned int bucket_size; + + memset(buckets, 0, sizeof(buckets)); + + /* + * We work with discrete data buckets smaller than 1 does not make + * sense as well as it's a good idea to keep buckets integer sized + * to avoid scaling artifacts. + */ + bucket_size = MAX(1u, ceilu(1.00 * (max_sample - min_sample)/(rows-1))); + + for (i = 0; i < cur_sample; i++) { + unsigned int bucket; + bucket = flooru(1.00 * (samples[i] - min_sample)/bucket_size); + buckets[bucket]++; + } + + unsigned int max_bucket = buckets[0]; + for (i = 1; i < rows; i++) + max_bucket = MAX(max_bucket, buckets[i]); + + fprintf(stderr, "\n%*s| Frequency\n", line_header_len - 2, table_heading); + + print_line('-', cols); + fputc('\n', stderr); + + unsigned int l, r; + + for (l = 0; l < rows; l++) { + if (buckets[l]) + break; + } + + for (r = rows-1; r > l; r--) { + if (buckets[r]) + break; + } + + for (i = l; i <= r; i++) { + float len = bucket_len(buckets[i], max_bucket, plot_line_len); + + fprintf(stderr, "%*lli | ", + line_header_len - 3, min_sample + bucket_size*i); + print_line('*', len); + + if ((len - (int)len) >= 0.5) + fputc('+', stderr); + else if ((len - (int)len) >= 0.25) + fputc('-', stderr); + else if (len < 0.25 && buckets[i]) + fputc('.', stderr); + + fputc('\n', stderr); + } + + print_line('-', cols); + fputc('\n', stderr); + + float scale = 1.00 * plot_line_len / max_bucket; + + fprintf(stderr, + "%*uus | 1 sample = %.5f '*', %.5f '+', %.5f '-', non-zero '.'\n", + line_header_len - 5, bucket_size, scale, scale * 2, scale * 4); + + fputc('\n', stderr); +} + +void tst_timer_sample(void) +{ + samples[cur_sample++] = tst_timer_elapsed_us(); +} + +static int cmp(const void *a, const void *b) +{ + const long long *aa = a, *bb = b; + + return (*bb - *aa); +} + +/* + * The threshold per one syscall is computed as a sum of: + * + * 400 us - accomodates for context switches, process + * migrations between CPUs on SMP, etc. + * 2*monotonic_resolution - accomodates for granurality of the CLOCK_MONOTONIC + * slack_per_scall - max of 0.1% of the sleep capped on 100ms or + * current->timer_slack_ns, which is slack allowed + * in kernel + * + * The formula for slack_per_scall applies to select() and *poll*() syscalls, + * the futex and *nanosleep() use only the timer_slack_ns, so we are a bit + * less strict here that we could be for these two for longer sleep times... + * + * We also allow for outliners, i.e. add some number to the threshold in case + * that the number of iteration is small. For large enoung number of iterations + * outliners are discarded and averaged out. + */ +static long long compute_threshold(long long requested_us, + unsigned int nsamples) +{ + unsigned int slack_per_scall = MIN(100000, requested_us / 1000); + + slack_per_scall = MAX(slack_per_scall, timerslack); + + return (400 + 2 * monotonic_resolution + slack_per_scall) * nsamples + + 3000/nsamples; +} + +/* + * Returns number of samples to discard. + * + * We set it to either at least 1 if number of samples > 1 or 5%. + */ +static unsigned int compute_discard(unsigned int nsamples) +{ + if (nsamples == 1) + return 0; + + return MAX(1u, nsamples / 20); +} + +static void write_to_file(void) +{ + unsigned int i; + FILE *f; + + if (!file_name) + return; + + f = fopen(file_name, "w"); + + if (!f) { + tst_res(TWARN | TERRNO, + "Failed to open '%s'", file_name); + return; + } + + for (i = 0; i < cur_sample; i++) + fprintf(f, "%lli\n", samples[i]); + + if (fclose(f)) { + tst_res(TWARN | TERRNO, + "Failed to close file '%s'", file_name); + } +} + + +/* + * Timer testing function. + * + * What we do here is: + * + * * Take nsamples measurements of the timer function, the function + * to be sampled is defined in the the actual test. + * + * * We sort the array of samples, then: + * + * - look for outliners which are samples where the sleep time has exceeded + * requested sleep time by an order of magnitude and, at the same time, are + * greater than clock resolution multiplied by three. + * + * - check for samples where the call has woken up too early which is a plain + * old bug + * + * - then we compute truncated mean and compare that with the requested sleep + * time increased by a threshold + */ +void do_timer_test(long long usec, unsigned int nsamples) +{ + long long trunc_mean, median; + unsigned int discard = compute_discard(nsamples); + unsigned int keep_samples = nsamples - discard; + long long threshold = compute_threshold(usec, keep_samples); + int i; + int failed = 0; + + tst_res(TINFO, + "%s sleeping for %llius %u iterations, threshold %.2fus", + scall, usec, nsamples, 1.00 * threshold / (keep_samples)); + + cur_sample = 0; + for (i = 0; i < (int)nsamples; i++) { + if (sample(CLOCK_MONOTONIC, usec)) { + tst_res(TINFO, "sampling function failed, exitting"); + return; + } + } + + qsort(samples, nsamples, sizeof(samples[0]), cmp); + + write_to_file(); + + for (i = 0; samples[i] > 10 * usec && i < (int)nsamples; i++) { + if (samples[i] <= 3 * monotonic_resolution) + break; + } + + if (i > 0) { + tst_res(TINFO, "Found %i outliners in [%lli,%lli] range", + i, samples[0], samples[i-1]); + } + + for (i = nsamples - 1; samples[i] < usec && i > -1; i--); + + if (i < (int)nsamples - 1) { + tst_res(TFAIL, "%s woken up early %u times range: [%lli,%lli]", + scall, nsamples - 1 - i, + samples[i+1], samples[nsamples-1]); + failed = 1; + } + + median = samples[nsamples/2]; + + trunc_mean = 0; + + for (i = discard; i < (int)nsamples; i++) + trunc_mean += samples[i]; + + tst_res(TINFO, + "min %llius, max %llius, median %llius, trunc mean %.2fus (discarded %u)", + samples[nsamples-1], samples[0], median, + 1.00 * trunc_mean / keep_samples, discard); + + if (virt_env) { + tst_res(TINFO, + "Virtualisation detected, skipping oversleep checks"); + } else if (trunc_mean > (nsamples - discard) * usec + threshold) { + tst_res(TFAIL, "%s slept for too long", scall); + + if (!print_frequency_plot) + frequency_plot(); + + failed = 1; + } + + if (print_frequency_plot) + frequency_plot(); + + if (!failed) + tst_res(TPASS, "Measured times are within thresholds"); +} + +static void parse_timer_opts(void); + +static int set_latency(void) +{ + int fd, latency = 0; + + fd = open("/dev/cpu_dma_latency", O_WRONLY); + if (fd < 0) + return fd; + + return write(fd, &latency, sizeof(latency)); +} + +static void timer_setup(void) +{ + struct timespec t; + int ret; + + if (setup) + setup(); + + /* + * Running tests in VM may cause timing issues, disable upper bound + * checks if any hypervisor is detected. + */ + virt_env = tst_is_virt(VIRT_ANY); + tst_clock_getres(CLOCK_MONOTONIC, &t); + + tst_res(TINFO, "CLOCK_MONOTONIC resolution %lins", (long)t.tv_nsec); + + monotonic_resolution = t.tv_nsec / 1000; + timerslack = 50; + +#ifdef PR_GET_TIMERSLACK + ret = prctl(PR_GET_TIMERSLACK); + if (ret < 0) { + tst_res(TINFO, "prctl(PR_GET_TIMERSLACK) = -1, using %uus", + timerslack); + } else { + timerslack = ret / 1000; + tst_res(TINFO, "prctl(PR_GET_TIMERSLACK) = %ius", timerslack); + } +#else + tst_res(TINFO, "PR_GET_TIMERSLACK not defined, using %uus", + timerslack); +#endif /* PR_GET_TIMERSLACK */ + parse_timer_opts(); + + samples = SAFE_MALLOC(sizeof(long long) * MAX(MAX_SAMPLES, sample_cnt)); + if (set_latency() < 0) + tst_res(TINFO, "Failed to set zero latency constraint: %m"); +} + +static void timer_cleanup(void) +{ + free(samples); + + if (cleanup) + cleanup(); +} + +static struct tst_timer_tcase { + long long usec; + unsigned int samples; +} tcases[] = { + {1000, 500}, + {2000, 500}, + {5000, 300}, + {10000, 100}, + {25000, 50}, + {100000, 10}, + {1000000, 2}, +}; + +static void timer_test_fn(unsigned int n) +{ + do_timer_test(tcases[n].usec, tcases[n].samples); +} + +static void single_timer_test(void) +{ + do_timer_test(sleep_time, sample_cnt); +} + +static struct tst_option options[] = { + {"p", &print_frequency_plot, "-p Print frequency plot"}, + {"s:", &str_sleep_time, "-s us Sleep time"}, + {"n:", &str_sample_cnt, "-n uint Number of samples to take"}, + {"f:", &file_name, "-f fname Write measured samples into a file"}, + {NULL, NULL, NULL} +}; + +static void parse_timer_opts(void) +{ + if (str_sleep_time) { + if (tst_parse_int(str_sleep_time, &sleep_time, 0, INT_MAX)) { + tst_brk(TBROK, + "Invalid sleep time '%s'", str_sleep_time); + } + } + + if (str_sample_cnt) { + if (tst_parse_int(str_sample_cnt, &sample_cnt, 1, INT_MAX)) { + tst_brk(TBROK, + "Invalid sample count '%s'", str_sample_cnt); + } + } + + if (str_sleep_time || str_sample_cnt) { + if (sleep_time < 0) + sleep_time = 10000; + + if (!sample_cnt) + sample_cnt = 500; + + long long timeout = sleep_time * sample_cnt / 1000000; + + tst_set_timeout(timeout + timeout/10); + + test->test_all = single_timer_test; + test->test = NULL; + test->tcnt = 0; + } +} + +struct tst_test *tst_timer_test_setup(struct tst_test *timer_test) +{ + setup = timer_test->setup; + cleanup = timer_test->cleanup; + scall = timer_test->scall; + sample = timer_test->sample; + + timer_test->scall = NULL; + timer_test->setup = timer_setup; + timer_test->cleanup = timer_cleanup; + timer_test->test = timer_test_fn; + timer_test->tcnt = ARRAY_SIZE(tcases); + timer_test->sample = NULL; + timer_test->options = options; + + test = timer_test; + + return timer_test; +} |