From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Martin Kepplinger <martin.kepplinger@puri.sm>,
viresh.kumar@linaro.org, kevin.wangtao@linaro.org,
leo.yan@linaro.org, edubezval@gmail.com,
vincent.guittot@linaro.org, javi.merino@kernel.org,
rui.zhang@intel.com, daniel.thompson@linaro.org
Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 6/7] thermal/drivers/cpu_cooling: Introduce the cpu idle cooling driver
Date: Mon, 5 Aug 2019 09:37:43 +0200 [thread overview]
Message-ID: <2d7f1caa-351a-8fdc-bb6b-151f7313a042@linaro.org> (raw)
In-Reply-To: <20190805051111.24318-1-martin.kepplinger@puri.sm>
On 05/08/2019 07:11, Martin Kepplinger wrote:
> ---
[ ... ]
>> +static s64 cpuidle_cooling_runtime(struct cpuidle_cooling_device *idle_cdev)
>> +{
>> + s64 next_wakeup;
>> + unsigned long state = idle_cdev->state;
>> +
>> + /*
>> + * The function should not be called when there is no
>> + * mitigation because:
>> + * - that does not make sense
>> + * - we end up with a division by zero
>> + */
>> + if (!state)
>> + return 0;
>> +
>> + next_wakeup = (s64)((idle_cdev->idle_cycle * 100) / state) -
>> + idle_cdev->idle_cycle;
>> +
>> + return next_wakeup * NSEC_PER_USEC;
>> +}
>> +
>
> There is a bug in your calculation formula here when "state" becomes 100.
> You return 0 for the injection rate, which is the same as "rate" being 0,
> which is dangerous. You stop cooling when it's most necessary :)
Right, thanks for spotting this.
> I'm not sure how much sense really being 100% idle makes, so I, when testing
> this, just say if (state == 100) { state = 99 }. Anyways, just don't return 0.
>
> Daniel, thanks a lot for these additions! Could you send an update of this?
Yes, I'm working on a new version.
> btw, that's what I'm referring to:
> https://lore.kernel.org/linux-pm/1522945005-7165-1-git-send-email-daniel.lezcano@linaro.org/
> I know it's a little old already, but it seems like there hasn't been any
> equivalent solution in the meantime, has it?
>
> Using cpuidle for cooling is way more effective than cpufreq (which often
> hardly is).
On which platform that happens?
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next prev parent reply other threads:[~2019-08-05 7:37 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-05 16:16 [PATCH v3 0/7] CPU cooling device new strategies Daniel Lezcano
2018-04-05 16:16 ` [PATCH v3 1/7] thermal/drivers/cpu_cooling: Fixup the header and copyright Daniel Lezcano
[not found] ` <20180411061514.GL7671@vireshk-i7>
2018-04-11 8:56 ` Daniel Lezcano
2018-04-05 16:16 ` [PATCH v3 2/7] thermal/drivers/cpu_cooling: Add Software Package Data Exchange (SPDX) Daniel Lezcano
2018-04-05 16:16 ` [PATCH v3 3/7] thermal/drivers/cpu_cooling: Remove pointless field Daniel Lezcano
2018-04-05 16:16 ` [PATCH v3 4/7] thermal/drivers/Kconfig: Convert the CPU cooling device to a choice Daniel Lezcano
[not found] ` <20180411061851.GM7671@vireshk-i7>
2018-04-11 8:58 ` Daniel Lezcano
2018-04-05 16:16 ` [PATCH v3 5/7] thermal/drivers/cpu_cooling: Add idle cooling device documentation Daniel Lezcano
2018-04-05 16:16 ` [PATCH v3 6/7] thermal/drivers/cpu_cooling: Introduce the cpu idle cooling driver Daniel Lezcano
2018-04-11 8:51 ` Viresh Kumar
2018-04-11 9:29 ` Daniel Lezcano
2018-04-13 11:23 ` Sudeep Holla
2018-04-13 11:47 ` Daniel Lezcano
2018-04-16 7:37 ` Viresh Kumar
2018-04-16 7:44 ` Daniel Lezcano
2018-04-16 9:34 ` Sudeep Holla
2018-04-16 9:37 ` Viresh Kumar
2018-04-16 9:45 ` Daniel Lezcano
2018-04-16 9:50 ` Viresh Kumar
2018-04-16 10:03 ` Daniel Lezcano
2018-04-16 10:10 ` Viresh Kumar
2018-04-16 12:10 ` Daniel Lezcano
2018-04-16 12:30 ` Lorenzo Pieralisi
2018-04-16 13:57 ` Daniel Lezcano
2018-04-16 14:22 ` Lorenzo Pieralisi
2018-04-17 7:17 ` Daniel Lezcano
2018-04-17 10:24 ` Lorenzo Pieralisi
2018-04-16 12:31 ` Sudeep Holla
2018-04-16 12:49 ` Daniel Lezcano
2018-04-16 13:03 ` Sudeep Holla
2018-04-16 12:29 ` Sudeep Holla
2018-04-13 11:38 ` Daniel Thompson
2018-04-13 11:46 ` Daniel Lezcano
2019-08-05 5:11 ` Martin Kepplinger
2019-08-05 6:53 ` Martin Kepplinger
2019-08-05 7:39 ` Daniel Lezcano
2019-08-05 7:42 ` Martin Kepplinger
2019-08-05 7:58 ` Daniel Lezcano
2019-10-25 11:22 ` Martin Kepplinger
2019-10-25 14:45 ` Daniel Lezcano
2019-10-26 18:23 ` Martin Kepplinger
2019-10-28 15:16 ` Daniel Lezcano
2019-08-05 7:37 ` Daniel Lezcano [this message]
2019-08-05 7:40 ` Martin Kepplinger
2018-04-05 16:16 ` [PATCH v3 7/7] cpuidle/drivers/cpuidle-arm: Register the cooling device Daniel Lezcano
2018-04-11 8:51 ` Viresh Kumar
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