linux-kernel - Re: [PATCH V2 1/3] Calculate Thermal Pressure

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Message-ID: <20190425105658.q45cmfogrt6wwtih@queper01-ThinkPad-T460s>
Date:   Thu, 25 Apr 2019 11:57:00 +0100
From:   Quentin Perret <quentin.perret@....com>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     mingo@...hat.com, peterz@...radead.org, rui.zhang@...el.com,
        linux-kernel@...r.kernel.org, amit.kachhap@...il.com,
        viresh.kumar@...aro.org, javi.merino@...nel.org,
        edubezval@...il.com, daniel.lezcano@...aro.org,
        vincent.guittot@...aro.org, nicolas.dechesne@...aro.org,
        bjorn.andersson@...aro.org, dietmar.eggemann@....com
Subject: Re: [PATCH V2 1/3] Calculate Thermal Pressure

On Tuesday 16 Apr 2019 at 15:38:39 (-0400), Thara Gopinath wrote:
> +/* Per cpu structure to keep track of Thermal Pressure */
> +struct thermal_pressure {
> +	unsigned long scale; /* scale reflecting average cpu max capacity*/
> +	unsigned long acc_scale; /* Accumulated scale for this time window */
> +	unsigned long old_scale; /* Scale value for the previous window */
> +	unsigned long raw_scale; /* Raw max capacity */
> +	unsigned long age_stamp; /* Last time old_scale was updated */
> +	unsigned long last_update; /* Last time acc_scale was updated */
> +	spinlock_t lock; /* Lock for protecting from simultaneous access*/
> +	/* Timer for periodic update of thermal pressure */
> +	struct timer_list timer;

Do you actually need the periodic update ? You only really need to
update the 'scale' value when updating the LB stats no ? Nobody
accesses that value in between two LBs.

Thanks,
Quentin