linux-kernel - Re: [PATCH v4 5/7] cpufreq: Calculate number of busy CPUs

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Date:	Thu, 27 Jun 2013 15:06:43 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Lukasz Majewski <l.majewski@...sung.com>
Cc:	"Rafael J. Wysocky" <rjw@...k.pl>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Jonghwa Lee <jonghwa3.lee@...sung.com>,
	Myungjoo Ham <myungjoo.ham@...sung.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Lukasz Majewski <l.majewski@...ess.pl>,
	Andre Przywara <andre.przywara@...aro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <eduardo.valentin@...com>
Subject: Re: [PATCH v4 5/7] cpufreq: Calculate number of busy CPUs

On 19 June 2013 22:42, Lukasz Majewski <l.majewski@...sung.com> wrote:
> In the core governor code, per cpu load value is calculated. This patch
> uses it to mark processor as a "busy" one, when load value is higher than
> 90%.

How can we take this assumption. What about a cpu which is only 70-80%
busy? So, we would be running at around 70% of policy->max.. Now at
this point you want to enable boost frequency and so that will happen for
all cores... Wouldn't that burn your chip?

> New cpufreq sysfs attribute is created (busy_cpus). It is read only
> and provides information about number of actually busy CPU.

Not required.

> diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
> index 077cea7..3402533 100644
> --- a/drivers/cpufreq/cpufreq_governor.c
> +++ b/drivers/cpufreq/cpufreq_governor.c
> @@ -148,6 +148,7 @@ void dbs_check_cpu(struct dbs_data *dbs_data, int cpu)
>                         continue;
>
>                 load = 100 * (wall_time - idle_time) / wall_time;
> +               cpufreq_set_busy_cpu(j, load > 90 ? 1 : 0);

do this only when boost is enabled.

>                 if (dbs_data->cdata->governor == GOV_ONDEMAND) {
>                         int freq_avg = __cpufreq_driver_getavg(policy, j);
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