From: Andy Tang <andy.tang@nxp.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: "rjw@rjwysocki.net" <rjw@rjwysocki.net>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>
Subject: RE: [EXT] Re: Ask for help about cpufreq issue
Date: Fri, 14 Feb 2020 10:00:19 +0000 [thread overview]
Message-ID: <VI1PR04MB4333A771266A447FB8682E2FF3150@VI1PR04MB4333.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <20200213084819.jveurrsvtv72ssug@vireshk-i7>
Hi Viresh,
> -----Original Message-----
> From: Viresh Kumar <viresh.kumar@linaro.org>
> Sent: 2020年2月13日 16:48
> To: Andy Tang <andy.tang@nxp.com>
> Cc: rjw@rjwysocki.net; linux-pm@vger.kernel.org
> Subject: Re: [EXT] Re: Ask for help about cpufreq issue
>
> On 13-02-20, 08:18, Andy Tang wrote:
> > I keep monitoring cpu usage for several minutes, by top and mpstat
> > tool, and found most of the cpus are 100% idle, once in a while one of the
> cpus increases the load to about 18%.
>
> I don't think top will be a good way for doing this test as we are talking about
> load on a CPU in interval in milliseconds. Please check with tracing and see
> what's keeping the CPU busy..
>
> > Technically if the cpu usage is not more than up_threshold(80), cpu
> > won't increase its frequency and keep at the lowest frequency when cpu is
> at the lowest frequency and conservative governor is used.
>
> I agree. Which means that there are some spikes of work getting scheduled
> on CPUs. The load will increase slowly and will also decrease slowly
> (step-by-step) with conservative governor.
>
> > So I can't understand why cpu frequency increased?
>
> Tracing or debugging cs_dbs_update() in conservative governor is the only
> way out I would suggest.
From cs_dbs_update() function, I did see that sometimes the LOAD is at 100% usage.
There is almost no application running. That must be some spikes of working running.
Unfortunately I can't track them by cs_dbs_update() or ftrace tool.
I doubt the ftrace can be used this way. Do you have any other suggestions? Maybe another tools?
BR,
Andy
>
> --
> viresh
next prev parent reply other threads:[~2020-02-14 10:00 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-07 5:09 Ask for help about cpufreq issue Andy Tang
2020-02-07 5:23 ` Viresh Kumar
2020-02-07 6:03 ` [EXT] " Andy Tang
2020-02-07 7:05 ` Viresh Kumar
2020-02-11 4:20 ` Andy Tang
2020-02-11 5:53 ` Viresh Kumar
2020-02-11 6:23 ` Andy Tang
2020-02-11 6:34 ` Viresh Kumar
2020-02-11 7:20 ` Andy Tang
2020-02-12 10:11 ` Andy Tang
2020-02-12 11:50 ` Viresh Kumar
2020-02-13 8:18 ` Andy Tang
2020-02-13 8:48 ` Viresh Kumar
2020-02-13 9:12 ` Andy Tang
2020-02-13 9:15 ` Viresh Kumar
2020-02-13 9:21 ` Andy Tang
2020-02-14 10:00 ` Andy Tang [this message]
2020-02-17 8:22 ` Viresh Kumar
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