From: Chao Gao <chao.gao@intel.com>
To: lkp@lists.01.org
Subject: Re: [clocksource] 8901ecc231: stress-ng.lockbus.ops_per_sec -9.5% regression
Date: Thu, 05 Aug 2021 13:39:40 +0800 [thread overview]
Message-ID: <20210805053938.GA12593@gao-cwp> (raw)
In-Reply-To: <20210805040349.GD4397@paulmck-ThinkPad-P17-Gen-1>
[-- Attachment #1: Type: text/plain, Size: 1064 bytes --]
[snip]
>> This patch works well; no false-positive (marking TSC unstable) in a
>> 10hr stress test.
>
>Very good, thank you! May I add your Tested-by?
sure.
Tested-by: Chao Gao <chao.gao@intel.com>
>
>I expect that I will need to modify the patch a bit more to check for
>a system where it is -never- able to get a good fine-grained read from
>the clock.
Agreed.
>And it might be that your test run ended up in that state.
Not that case judging from kernel logs. Coarse-grained check happened 6475
times in 43k seconds (by grep "coarse-grained skew check" in kernel logs).
So, still many checks were fine-grained.
>
>My current thought is that if more than (say) 100 consecutive attempts
>to read the clocksource get hit with excessive delays, it is time to at
>least do a WARN_ON(), and maybe also time to disable the clocksource
>due to skew. The reason is that if reading the clocksource -always-
>sees excessive delays, perhaps the clock driver or hardware is to blame.
>
>Thoughts?
It makes sense to me.
Thanks
Chao
WARNING: multiple messages have this Message-ID (diff)
From: Chao Gao <chao.gao@intel.com>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Feng Tang <feng.tang@intel.com>,
kernel test robot <oliver.sang@intel.com>,
John Stultz <john.stultz@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Stephen Boyd <sboyd@kernel.org>, Jonathan Corbet <corbet@lwn.net>,
Mark Rutland <Mark.Rutland@arm.com>,
Marc Zyngier <maz@kernel.org>, Andi Kleen <ak@linux.intel.com>,
Xing Zhengjun <zhengjun.xing@linux.intel.com>,
Chris Mason <clm@fb.com>, LKML <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
lkp@lists.01.org, lkp@intel.com, ying.huang@intel.com,
zhengjun.xing@intel.com
Subject: Re: [clocksource] 8901ecc231: stress-ng.lockbus.ops_per_sec -9.5% regression
Date: Thu, 5 Aug 2021 13:39:40 +0800 [thread overview]
Message-ID: <20210805053938.GA12593@gao-cwp> (raw)
In-Reply-To: <20210805040349.GD4397@paulmck-ThinkPad-P17-Gen-1>
[snip]
>> This patch works well; no false-positive (marking TSC unstable) in a
>> 10hr stress test.
>
>Very good, thank you! May I add your Tested-by?
sure.
Tested-by: Chao Gao <chao.gao@intel.com>
>
>I expect that I will need to modify the patch a bit more to check for
>a system where it is -never- able to get a good fine-grained read from
>the clock.
Agreed.
>And it might be that your test run ended up in that state.
Not that case judging from kernel logs. Coarse-grained check happened 6475
times in 43k seconds (by grep "coarse-grained skew check" in kernel logs).
So, still many checks were fine-grained.
>
>My current thought is that if more than (say) 100 consecutive attempts
>to read the clocksource get hit with excessive delays, it is time to at
>least do a WARN_ON(), and maybe also time to disable the clocksource
>due to skew. The reason is that if reading the clocksource -always-
>sees excessive delays, perhaps the clock driver or hardware is to blame.
>
>Thoughts?
It makes sense to me.
Thanks
Chao
next prev parent reply other threads:[~2021-08-05 5:39 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-21 8:33 [clocksource] 8901ecc231: stress-ng.lockbus.ops_per_sec -9.5% regression kernel test robot
2021-05-21 8:33 ` kernel test robot
2021-05-21 13:56 ` Paul E. McKenney
2021-05-21 13:56 ` Paul E. McKenney
2021-05-22 16:08 ` Paul E. McKenney
2021-05-22 16:08 ` Paul E. McKenney
2021-05-26 6:49 ` Feng Tang
2021-05-26 6:49 ` Feng Tang
2021-05-26 13:49 ` Paul E. McKenney
2021-05-26 13:49 ` Paul E. McKenney
2021-05-27 18:29 ` Paul E. McKenney
2021-05-27 18:29 ` Paul E. McKenney
2021-05-27 19:01 ` Andi Kleen
2021-05-27 19:01 ` Andi Kleen
2021-05-27 19:19 ` Paul E. McKenney
2021-05-27 19:19 ` Paul E. McKenney
2021-05-27 19:29 ` Matthew Wilcox
2021-05-27 19:29 ` Matthew Wilcox
2021-05-27 21:05 ` Paul E. McKenney
2021-05-27 21:05 ` Paul E. McKenney
2021-05-28 0:58 ` Andi Kleen
2021-05-28 0:58 ` Andi Kleen
2021-06-01 17:10 ` Paul E. McKenney
2021-06-01 17:10 ` Paul E. McKenney
2021-08-02 6:20 ` Chao Gao
2021-08-02 6:20 ` Chao Gao
2021-08-02 17:02 ` Paul E. McKenney
2021-08-02 17:02 ` Paul E. McKenney
2021-08-03 8:58 ` Chao Gao
2021-08-03 8:58 ` Chao Gao
2021-08-03 13:48 ` Paul E. McKenney
2021-08-03 13:48 ` Paul E. McKenney
2021-08-05 2:16 ` Chao Gao
2021-08-05 2:16 ` Chao Gao
2021-08-05 4:03 ` Paul E. McKenney
2021-08-05 4:03 ` Paul E. McKenney
2021-08-05 4:34 ` Andi Kleen
2021-08-05 4:34 ` Andi Kleen
2021-08-05 15:33 ` Paul E. McKenney
2021-08-05 15:33 ` Paul E. McKenney
2021-08-05 5:39 ` Chao Gao [this message]
2021-08-05 5:39 ` Chao Gao
2021-08-05 15:37 ` Paul E. McKenney
2021-08-05 15:37 ` Paul E. McKenney
2021-08-06 2:10 ` Chao Gao
2021-08-06 2:10 ` Chao Gao
2021-08-06 4:15 ` Paul E. McKenney
2021-08-06 4:15 ` Paul E. McKenney
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