linux-kernel - Re: CPU isolation question again

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Message-ID: <CAJRGBZzn66mpQo+PCQirzqE=Wdm9T7Z01P20FQsHQnTPEd2mqA@mail.gmail.com>
Date:	Wed, 4 Jul 2012 20:42:29 +0800
From:	Luming Yu <luming.yu@...il.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, gilad@...yossef.com,
	Len Brown <lenb@...nel.org>, shli@...nel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: CPU isolation question again

On Tue, Jul 3, 2012 at 7:28 PM, Frederic Weisbecker <fweisbec@...il.com> wrote:
> On Wed, Jun 27, 2012 at 09:22:09PM +0800, Luming Yu wrote:
>> Hi there,
>>
>> I noticed some discussion about CPU isolation which points me to the
>> patch set (https://lkml.org/lkml/2011/8/15/245). I'm currently
>> preparing a RFC-patch-set to automatically pick up a few suitable CPUs
>> to isolate then kick them out of service for a while. We need to
>> balance between  thermal & power management And overall system
>> performance during this operation as much as possible. So
>> software-cpu-online-offline interface could not be a good option to
>> me. But to make sure I'm not blindly running on a dead-end path, I'd
>> check with experts here to ensure it makes some sense to isolate CPUs
>> to this level, and the idea also makes some sense, and the most
>> important is it's not implemented yet.
>
> I don't understand what you are trying to do and how exactly. How do you
> plan to do this isolation and how do you want to balance between thermal
> and power?

My question could be wrong as the question arose several weeks ago
when I came across
 drivers/acpi/acpi_paid.c which looks like a real user who need to
request system automatically
pick up a few CPU to get them isolated and deactivated. Later on, I
noticed tglx's cpu hot plug re-work.
I realized we could reuse the interface to do isolation and deactivation work.

Of cause, to pick up which ones to isolate and deactivate is another problem.

cc'ed the author and ACPI maintainer of the driver as well as tglx.

thanks!
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