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From: Viresh Kumar <viresh.kumar@linaro.org>
To: Andy Tang <andy.tang@nxp.com>
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: Thu, 13 Feb 2020 14:18:19 +0530	[thread overview]
Message-ID: <20200213084819.jveurrsvtv72ssug@vireshk-i7> (raw)
In-Reply-To: <VI1PR04MB43332FB8B9FAD91160D91A0CF31A0@VI1PR04MB4333.eurprd04.prod.outlook.com>

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.

-- 
viresh

  reply	other threads:[~2020-02-13  8:48 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 [this message]
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
2020-02-17  8:22                         ` Viresh Kumar

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