On Tue, Jun 23, 2026 at 01:32:08PM +0800, Tao Cui wrote: > > Hi Joe, > > One comment on the fallback: > > quota_usec = hz != -1 ? USEC_PER_SEC / hz : 1000; > > When HZ can't be determined (no CONFIG_IKCONFIG_PROC, or zcat missing), > the fallback to 1000 is the exact value that fails at low HZ — so this > doesn't actually fix such kernels. A larger fallback (e.g. 10000, the > HZ=100 equivalent) would make the tests robust regardless of whether the > config is exposed.
Hi Tao Cui, Thank you for your review. I am happy to use 10000 as the fallback value. I will address this as well as the sashiko comments in v3. Thanks, Joe > > 在 2026/6/23 03:43, Joe Simmons-Talbott 写道: > > For lower HZ values a quota of 1000us is much lower than the amount > > of microseconds per tick which makes the tests test_cpucg_max and > > test_cpugc_max_nested fail. Use the amount of microseconds per tick > > as the quota value. > > > > Signed-off-by: Joe Simmons-Talbott <[email protected]> > > --- > > changes since v1: > > - Try checking /proc/config.gz to get the actual kernel HZ value and > > fallback to 1000 if the value cannot be determined. > > > > tools/testing/selftests/cgroup/test_cpu.c | 33 +++++++++++++++++++++-- > > 1 file changed, 31 insertions(+), 2 deletions(-) > > > > diff --git a/tools/testing/selftests/cgroup/test_cpu.c > > b/tools/testing/selftests/cgroup/test_cpu.c > > index 7a40d76b9548..65e09555309f 100644 > > --- a/tools/testing/selftests/cgroup/test_cpu.c > > +++ b/tools/testing/selftests/cgroup/test_cpu.c > > @@ -639,6 +639,29 @@ test_cpucg_nested_weight_underprovisioned(const char > > *root) > > return run_cpucg_nested_weight_test(root, false); > > } > > > > +/* > > + * 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) > > +{ > > + long hz = -1; > > + FILE *f; > > + char cmd[256] = "zcat /proc/config.gz 2>/dev/null | grep '^CONFIG_HZ='"; > > + > > + f = popen(cmd, "r"); > > + > > + if (!f) > > + goto out; > > + > > + fscanf(f, "CONFIG_HZ=%ld", &hz); > > + > > +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. > > @@ -646,7 +669,8 @@ test_cpucg_nested_weight_underprovisioned(const char > > *root) > > static int test_cpucg_max(const char *root) > > { > > int ret = KSFT_FAIL; > > - long quota_usec = 1000; > > + long hz = _get_config_hz(); > > + long quota_usec; > > long default_period_usec = 100000; /* cpu.max's default period */ > > long duration_seconds = 1; > > > > @@ -655,6 +679,8 @@ static int test_cpucg_max(const char *root) > > char *cpucg; > > char quota_buf[32]; > > > > + quota_usec = hz != -1 ? USEC_PER_SEC / hz : 1000; > > + > > snprintf(quota_buf, sizeof(quota_buf), "%ld", quota_usec); > > > > cpucg = cg_name(root, "cpucg_test"); > > @@ -710,7 +736,8 @@ static int test_cpucg_max(const char *root) > > static int test_cpucg_max_nested(const char *root) > > { > > int ret = KSFT_FAIL; > > - long quota_usec = 1000; > > + long quota_usec; > > + long hz = _get_config_hz(); > > long default_period_usec = 100000; /* cpu.max's default period */ > > long duration_seconds = 1; > > > > @@ -719,6 +746,8 @@ static int test_cpucg_max_nested(const char *root) > > char *parent, *child; > > char quota_buf[32]; > > > > + quota_usec = hz != -1 ? USEC_PER_SEC / hz : 1000; > > + > > snprintf(quota_buf, sizeof(quota_buf), "%ld", quota_usec); > > > > parent = cg_name(root, "cpucg_parent"); > >
