linux-kernel - RE: [PATCH] clocksource: Print clocksource name when clocksource is tested unstable

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Date:   Thu, 17 Nov 2022 08:03:07 +0000
From:   "Sun, Yunying" <yunying.sun@...el.com>
To:     "Tang, Feng" <feng.tang@...el.com>
CC:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "paulmck@...nel.org" <paulmck@...nel.org>,
        "longman@...hat.com" <longman@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] clocksource: Print clocksource name when clocksource is
 tested unstable

Hi Feng,

For the "tsc fall back to hpet" issue, thanks a lot for pointing me to the fix proposal patch earlier:
 https://lore.kernel.org/lkml/20221021062131.1826810-1-feng.tang@intel.com/ .

I shared this patch set to our customer yesterday. 
Just got feedback that customer has verified the "tsc fall back to hpet" issue does not appear anymore with this patch set, after 24hrs stress test on 8 servers.

-Yunying

-----Original Message-----
From: Tang, Feng <feng.tang@...el.com> 
Sent: Thursday, 17 November, 2022 14:47
To: Sun, Yunying <yunying.sun@...el.com>
Cc: tglx@...utronix.de; peterz@...radead.org; paulmck@...nel.org; longman@...hat.com; x86@...nel.org; linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clocksource: Print clocksource name when clocksource is tested unstable

On Wed, Nov 16, 2022 at 04:22:21PM +0800, Yunying Sun wrote:
> Some "TSC fall back to HPET" cases are seen on systems that have more 
> than 2 numa nodes. When this happens, in kernel log it has:

Hi Yunying,

If the system's physical sockests number <= 2, I would suggest you to try the patch https://lore.kernel.org/lkml/20221021062131.1826810-1-feng.tang@intel.com/,
which is still under review and discussion.

Thanks,
Feng

> clocksource: timekeeping watchdog on CPU168: hpet read-back delay of 
> 4296200ns, attempt 4, marking unstable
> 
> The "hpet" here is misleading since it prints only the name of 
> watchdog, where actually it's measuring the delay of 3 reads: wd-clocksource-wd.
> 
> Signed-off-by: Yunying Sun <yunying.sun@...el.com>
> ---
>  kernel/time/clocksource.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c 
> index 8058bec87ace..fac8c0d90e61 100644
> --- a/kernel/time/clocksource.c
> +++ b/kernel/time/clocksource.c
> @@ -257,8 +257,8 @@ static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow,
>  			goto skip_test;
>  	}
>  
> -	pr_warn("timekeeping watchdog on CPU%d: %s read-back delay of %lldns, attempt %d, marking unstable\n",
> -		smp_processor_id(), watchdog->name, wd_delay, nretries);
> +	pr_warn("timekeeping watchdog on CPU%d: wd-%s-wd read-back delay of %lldns, attempt %d, marking unstable\n",
> +		smp_processor_id(), cs->name, wd_delay, nretries);
>  	return WD_READ_UNSTABLE;
>  
>  skip_test:
> --
> 2.17.0
>