linux-kernel - Re: [PATCH] cpufreq: Don't destroy/realloc policy/sysfs on hotplug/suspend

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Date:	Wed, 23 Jul 2014 20:02:15 -0700
From:	Saravana Kannan <skannan@...eaurora.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	Viresh Kumar <viresh.kumar@...aro.org>,
	Todd Poynor <toddpoynor@...gle.com>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] cpufreq: Don't destroy/realloc policy/sysfs on hotplug/suspend

On 07/16/2014 03:02 PM, Rafael J. Wysocki wrote:
> On Wednesday, July 09, 2014 07:37:30 PM Saravana Kannan wrote:
>> Preliminary patch. Not tested. Just sending out to give an idea of what I'm
>> looking to do. Expect a lot more simplification when it's done.
>>
>> Benefits:
>> * A lot more simpler code.
>> * Less stability issues.
>> * Suspend/resume time would improve.
>> * Hotplug time would improve.
>> * Sysfs file permissions would be maintained.
>> * More policy settings would be maintained across suspend/resume.
>> * cpufreq stats would be maintained across hotplug for all CPUs.
>
> One problem.  The real hotplug (when the CPU actually goes away) depends on
> offline removing all that stuff for it.  How are you going to address that?
>

Ok, I think I've figured this out. But one question. Is it possible to 
physically remove one CPU in a bunch of "related cpus" without also 
unplugging the rest? Put another way, can you unplug one core from a 
cluster?

It's not too hard to support that too, but if it's not a realistic case, 
I would rather not write code for that.

-Saravana

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