From: "Michal Koutný" <mkoutny@suse.com>
To: kernel test robot <oliver.sang@intel.com>
Cc: Shashank Balaji <shashank.mahadasyam@sony.com>,
oe-lkp@lists.linux.dev, lkp@intel.com,
linux-kernel@vger.kernel.org, Tejun Heo <tj@kernel.org>,
cgroups@vger.kernel.org
Subject: Re: [linus:master] [selftests/cgroup] 954bacce36: kernel-selftests.cgroup.test_cpu.test_cpucg_max.fail
Date: Mon, 11 Aug 2025 23:32:13 +0200 [thread overview]
Message-ID: <lsnebzejrxrpulxxmyvkfdrsplbi2ft2n5zuux3dl3ewt5ihrs@j3umrzndddsb> (raw)
In-Reply-To: <202508070722.46239e7c-lkp@intel.com>
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Hello.
On Thu, Aug 07, 2025 at 01:52:31PM +0800, kernel test robot <oliver.sang@intel.com> wrote:
> dfe25fbaedfc2a07 954bacce36d976fe472090b5598
> ---------------- ---------------------------
> fail:runs %reproduction fail:runs
> | | |
> :6 100% 6:6 kernel-selftests.cgroup.test_cpu.test_cpucg_max.fail
> :6 100% 6:6 kernel-selftests.cgroup.test_cpu.test_cpucg_max_nested.fail
>
>
> not sure if there are any necessary env setting? thanks
The selftest commit essentially changed the tolerance margin from
ridiculously large to something that looked statistically appropriate
[1].
However, when I run the test (30x) on the 954bacce36 I get:
quantile([D1 D2 D8]) # 1 2 and 8 vCPUs respectively
ans =
1.3086e+04 1.1559e+04 1.1177e+04 # min
1.5109e+04 1.2936e+04 1.2989e+04
1.5791e+04 1.3938e+04 1.3788e+04 # median
1.6159e+04 1.5385e+04 1.4980e+04
1.8757e+04 1.8699e+04 1.9494e+04 # max
I obtain similar values also on v6.15 (the kernel + 954bacce36
selftest). So it's not anything in throtlling implementation affecting
this.
The tests above were with HZ=250, for HZ=1000, I get slightly smaller
results with D2:
1.1753e+04 # min
1.2634e+04
1.3208e+04 # median
1.4010e+04
1.6937e+04 # max
But still nowhere the 20% margin (i.e. values_close(...10%)), these
values would demand up to 100% (values_close(..., 50%)). Or add a bias
derived from sched_cfs_bandwidth_slice_us or increase the tested quota
from 1% to 5%, that'd be an improvement:
48882 # min
52450
52941 # median
54284 # 75th percentile
73186 # max (limit would be 60000)
I'm not sure how big overrun we want to accept as a pass.
Michal
[1] lore.kernel.org/r/20250701-kselftest-cgroup-fix-cpu-max-v1-2-049507ad6832@sony.com
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prev parent reply other threads:[~2025-08-11 21:32 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-07 5:52 [linus:master] [selftests/cgroup] 954bacce36: kernel-selftests.cgroup.test_cpu.test_cpucg_max.fail kernel test robot
2025-08-11 21:32 ` Michal Koutný [this message]
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