From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753911Ab2GDOgq (ORCPT ); Wed, 4 Jul 2012 10:36:46 -0400 Received: from mail-gh0-f174.google.com ([209.85.160.174]:39785 "EHLO mail-gh0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753518Ab2GDOgp (ORCPT ); Wed, 4 Jul 2012 10:36:45 -0400 Date: Wed, 4 Jul 2012 16:36:39 +0200 From: Frederic Weisbecker To: Luming Yu Cc: LKML , gilad@benyossef.com, Len Brown , shli@kernel.org, Thomas Gleixner Subject: Re: CPU isolation question again Message-ID: <20120704143635.GE28294@somewhere> References: <20120703112828.GA28294@somewhere> <20120704132539.GD28294@somewhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 04, 2012 at 10:12:43PM +0800, Luming Yu wrote: > On Wed, Jul 4, 2012 at 9:25 PM, Frederic Weisbecker wrote: > > On Wed, Jul 04, 2012 at 08:42:29PM +0800, Luming Yu wrote: > >> On Tue, Jul 3, 2012 at 7:28 PM, Frederic Weisbecker 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. > > > > May be I'm confused because we both have our own definition of isolation. > > I'm not sure what kind of CPU isolation you're looking for. > > At first, it needs not avaiable to scheduler. Then, it needs in > deepest power saving mode. > At last, it needs available to scheduler again on demand. > Sounds very like a typical soft offline cpu, but needs to be low light weight. I see. So indeed the latest developments made in CPU hotplug could make it a solution for you.