Hi. On Wed, Jun 24, 2026 at 12:03:57PM -0400, Joe Simmons-Talbott <[email protected]> wrote: > +/* > + * Best effort attempt to get the kernel's HZ value from the config. > + * Return the HZ value if found otherwise return -1 to indicate failure. > + */ > +static long > +_get_config_hz(void)
drop underscore from the static function
> +{
> + long hz = -1;
use the default 1000 here to simplify the callers
> + FILE *f;
> + char cmd[256] = "zcat /proc/config.gz 2>/dev/null | grep '^CONFIG_HZ='";
> +
> + f = popen(cmd, "r");
> +
> + if (!f)
> + return hz;
> +
> + if (fscanf(f, "CONFIG_HZ=%ld", &hz) == EOF)
> + goto out;
> +
> +out:
> + pclose(f);
> + return hz;
> +}
> +
> /*
> * This test creates a cgroup with some maximum value within a period, and
> * verifies that a process in the cgroup is not overscheduled.
> @@ -646,15 +670,21 @@ test_cpucg_nested_weight_underprovisioned(const char
> *root)
> static int test_cpucg_max(const char *root)
> {
> int ret = KSFT_FAIL;
> + long hz = _get_config_hz();
> long quota_usec = 1000;
> long default_period_usec = 100000; /* cpu.max's default period */
> - long duration_seconds = 1;
> + long duration_seconds;
>
> - long duration_usec = duration_seconds * USEC_PER_SEC;
> + long duration_usec;
> long usage_usec, n_periods, remainder_usec, expected_usage_usec;
> char *cpucg;
> char quota_buf[32];
>
> + if (hz == -1)
> + hz = 1000;
> + duration_seconds = 1000 / hz;
> + duration_usec = duration_seconds * USEC_PER_SEC;
I'd do the calculation in usecs
duration_usec = duration_seconds * USEC_PER_SEC * 1000 / hz;
so that actual duration is more precise (for hz=300 which is the only
that doesn't divide 1000)
All in all, make the adjustments for HZ with less code (since I expect
this will need adjustments for SMPs in future).
Thanks,
Michal
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