[PATCH v2] Fix time/tst-cpuclock1 intermitent failures
Lucas A. M. Magalhaes
lamm@linux.ibm.com
Mon Feb 17 16:44:00 GMT 2020
Quoting Lucas A. M. Magalhaes (2020-02-06 11:48:19)
> This test fails intermittently in systems with heavy load as
> CLOCK_PROCESS_CPUTIME_ID is subject to scheduler pressure. Thus the
> test boundaries where relaxed to keep it from fail on this systems.
>
> A refactor of the spent time checking was made with some support
> functions. With the advantage to represent time jitter in percent
> of the target.
>
> The values used by the test boundaries are all empirical.
>
> ---
Ping.
>
> Hi,
>
> Please Carlos see if this is what you asked.
>
> I spent sometime gathering the spent times to find the values
> for the boundaries. From this I selected values that will fail less
> than 1% of the time, in the tested machines.
>
> Also as I found the spent time deviation completely asymmetrical
> I choose to separate the values in upper and lower bounds.
>
> changes from V2:
> - Add support functions
>
> support/Makefile | 1 +
> support/cpuclock.c | 51 ++++++++++++++++++++++++++++++++++++++++++++
> support/cpuclock.h | 30 ++++++++++++++++++++++++++
> time/tst-cpuclock1.c | 43 ++++++++++---------------------------
> 4 files changed, 93 insertions(+), 32 deletions(-)
> create mode 100644 support/cpuclock.c
> create mode 100644 support/cpuclock.h
>
> diff --git a/support/Makefile b/support/Makefile
> index 3325feb790..b308fe0856 100644
> --- a/support/Makefile
> +++ b/support/Makefile
> @@ -31,6 +31,7 @@ libsupport-routines = \
> check_dns_packet \
> check_hostent \
> check_netent \
> + cpuclock \
> delayed_exit \
> ignore_stderr \
> next_to_fault \
> diff --git a/support/cpuclock.c b/support/cpuclock.c
> new file mode 100644
> index 0000000000..f40c7e8d4a
> --- /dev/null
> +++ b/support/cpuclock.c
> @@ -0,0 +1,51 @@
> +/* Support functions for cpuclock tests.
> + Copyright (C) 2018-2020 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library 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
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <https://www.gnu.org/licenses/>. */
> +
> +#include "cpuclock.h"
> +#include <stdlib.h>
> +
> +#define T_1s 1000000000.0
> +
> +struct timespec time_normalize(struct timespec t) {
> + int diff;
> + diff = (t.tv_nsec / T_1s);
> + t.tv_sec += diff;
> + t.tv_nsec += -(diff * T_1s);
> + return t;
> +}
> +
> +struct timespec time_add(struct timespec a, struct timespec b) {
> + struct timespec s = {.tv_sec = a.tv_sec + b.tv_sec,
> + .tv_nsec = a.tv_nsec + b.tv_nsec};
> + return time_normalize(s);
> +}
> +
> +struct timespec time_sub(struct timespec a, struct timespec b) {
> + struct timespec d = {.tv_sec = a.tv_sec - b.tv_sec,
> + .tv_nsec = a.tv_nsec - b.tv_nsec};
> + return time_normalize(d);
> +}
> +
> +int percent_diff_check(struct timespec base, struct timespec dev,
> + float upper_bound, float lower_bound) {
> + double timea = base.tv_sec + base.tv_nsec / T_1s;
> + double timeb = dev.tv_sec + dev.tv_nsec / T_1s;
> + double diff = (timea - timeb) / (0.5 * (timea + timeb));
> + return (diff >= -upper_bound && diff <= lower_bound );
> +}
> +
> diff --git a/support/cpuclock.h b/support/cpuclock.h
> new file mode 100644
> index 0000000000..2505fbdcff
> --- /dev/null
> +++ b/support/cpuclock.h
> @@ -0,0 +1,30 @@
> +/* Support functions for cpuclock tests.
> + Copyright (C) 2018-2020 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library 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
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <https://www.gnu.org/licenses/>. */
> +
> +#ifndef SUPPORT_CPUCLOCK_H
> +#define SUPPORT_CPUCLOCK_H
> +
> +#include <time.h>
> +
> +struct timespec time_normalize(struct timespec t);
> +struct timespec time_add(struct timespec a, struct timespec b);
> +struct timespec time_sub(struct timespec a, struct timespec b);
> +int percent_diff_check(struct timespec base, struct timespec dev,
> + float upper_bound, float lower_bound);
> +
> +#endif /* SUPPORT_CPUCLOCK_H */
> diff --git a/time/tst-cpuclock1.c b/time/tst-cpuclock1.c
> index 0120906f23..4051de1646 100644
> --- a/time/tst-cpuclock1.c
> +++ b/time/tst-cpuclock1.c
> @@ -26,6 +26,7 @@
> #include <signal.h>
> #include <stdint.h>
> #include <sys/wait.h>
> +#include <support/cpuclock.h>
>
> /* This function is intended to rack up both user and system time. */
> static void
> @@ -155,19 +156,11 @@ do_test (void)
> printf ("live PID %d after sleep => %ju.%.9ju\n",
> child, (uintmax_t) after.tv_sec, (uintmax_t) after.tv_nsec);
>
> - struct timespec diff = { .tv_sec = after.tv_sec - before.tv_sec,
> - .tv_nsec = after.tv_nsec - before.tv_nsec };
> - if (diff.tv_nsec < 0)
> - {
> - --diff.tv_sec;
> - diff.tv_nsec += 1000000000;
> - }
> - if (diff.tv_sec != 0
> - || diff.tv_nsec > 600000000
> - || diff.tv_nsec < 100000000)
> + struct timespec diff = time_sub(after, before);
> + if (!percent_diff_check(sleeptime, diff, .3, 2))
> {
> printf ("before - after %ju.%.9ju outside reasonable range\n",
> - (uintmax_t) diff.tv_sec, (uintmax_t) diff.tv_nsec);
> + (uintmax_t) diff.tv_sec, (uintmax_t) diff.tv_nsec);
> result = 1;
> }
>
> @@ -194,19 +187,11 @@ do_test (void)
> }
> else
> {
> - struct timespec d = { .tv_sec = afterns.tv_sec - after.tv_sec,
> - .tv_nsec = afterns.tv_nsec - after.tv_nsec };
> - if (d.tv_nsec < 0)
> - {
> - --d.tv_sec;
> - d.tv_nsec += 1000000000;
> - }
> - if (d.tv_sec > 0
> - || d.tv_nsec < sleeptime.tv_nsec
> - || d.tv_nsec > sleeptime.tv_nsec * 2)
> + diff = time_sub(afterns, after);
> + if (!percent_diff_check(sleeptime, diff, .6, .34))
> {
> printf ("nanosleep time %ju.%.9ju outside reasonable range\n",
> - (uintmax_t) d.tv_sec, (uintmax_t) d.tv_nsec);
> + (uintmax_t) diff.tv_sec, (uintmax_t) diff.tv_nsec);
> result = 1;
> }
> }
> @@ -241,20 +226,14 @@ do_test (void)
> printf ("dead PID %d => %ju.%.9ju\n",
> child, (uintmax_t) dead.tv_sec, (uintmax_t) dead.tv_nsec);
>
> - diff.tv_sec = dead.tv_sec - after.tv_sec;
> - diff.tv_nsec = dead.tv_nsec - after.tv_nsec;
> - if (diff.tv_nsec < 0)
> - {
> - --diff.tv_sec;
> - diff.tv_nsec += 1000000000;
> - }
> - if (diff.tv_sec != 0 || diff.tv_nsec > 200000000)
> + diff = time_sub(dead, after);
> + sleeptime.tv_nsec = 100000000;
> + if (!percent_diff_check(sleeptime, diff, .6, .36))
> {
> printf ("dead - after %ju.%.9ju outside reasonable range\n",
> - (uintmax_t) diff.tv_sec, (uintmax_t) diff.tv_nsec);
> + (uintmax_t) diff.tv_sec, (uintmax_t) diff.tv_nsec);
> result = 1;
> }
> -
> /* Now reap the child and verify that its clock is no longer valid. */
> {
> int x;
> --
> 2.20.1
>
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