From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Lezcano Subject: Re: [PATCH 0/3] coupled cpuidle state support Date: Wed, 25 Jan 2012 15:04:18 +0100 Message-ID: <4F200BE2.2070301@free.fr> References: <1324426147-16735-1-git-send-email-ccross@android.com> <4F1929E9.7070707@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp6-g21.free.fr ([212.27.42.6]:45013 "EHLO smtp6-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754313Ab2AYOEc (ORCPT ); Wed, 25 Jan 2012 09:04:32 -0500 In-Reply-To: Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Colin Cross Cc: Daniel Lezcano , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pm@lists.linux-foundation.org, Len Brown , Kevin Hilman , Santosh Shilimkar , Amit Kucheria , Arjan van de Ven , Trinabh Gupta , Deepthi Dharwar , linux-omap@vger.kernel.org, linux-tegra@vger.kernel.org On 01/20/2012 09:40 PM, Colin Cross wrote: > On Fri, Jan 20, 2012 at 12:46 AM, Daniel Lezcano > wrote: >> Hi Colin, >> >> this patchset could be interesting to resolve in a generic way the cpu >> dependencies. >> What is the status of this patchset ? > I can't do much with it right now, because I don't have any devices > that can do SMP idle with a v3.2 kernel. I've started working on an > updated version that avoids the spinlock, but it might be a while > before I can test and post it. I'm mostly looking for feedback on the > approach taken in this patch, and whether it will be useful for other > SoCs besides Tegra and OMAP4. Hi Colin, I will be happy to test your patchset. Do you have a pointer to a more recent kernel ? >> Did you have the opportunity to measure the power consumption with and >> without this patchset ? > Power consumption will be very dependent on the specific SoC in > question. The most important factors are the power savings of the > independent cpuidle state (normally WFI) vs. the hotplug state > (normally 1 cpu in OFF), and the workload being tested. > > On a very idle system, these patches result in the same total power as > hotplugging one cpu and letting the other idle normally. On a 25% > busy system, you might see a slight increase in power, as the best > independent cpuidle state might be WFI, vs 1 cpu in OFF mode in > hotplug. On OMAP4, that difference is small, on the order of 10 mW. > Once you hit the threshold where a hotplug governor would have > hotplugged in the second cpu (lets say 40%), the savings from these > patches are enormous, as you can hit the lowest power state up to 60% > of the time, where the hotplug solution would never be going below WFI > on both cpus. On OMAP4, that can be well over 100 mW. Interesting. Thanks -- Daniel From mboxrd@z Thu Jan 1 00:00:00 1970 From: daniel.lezcano@free.fr (Daniel Lezcano) Date: Wed, 25 Jan 2012 15:04:18 +0100 Subject: [PATCH 0/3] coupled cpuidle state support In-Reply-To: References: <1324426147-16735-1-git-send-email-ccross@android.com> <4F1929E9.7070707@linaro.org> Message-ID: <4F200BE2.2070301@free.fr> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 01/20/2012 09:40 PM, Colin Cross wrote: > On Fri, Jan 20, 2012 at 12:46 AM, Daniel Lezcano > wrote: >> Hi Colin, >> >> this patchset could be interesting to resolve in a generic way the cpu >> dependencies. >> What is the status of this patchset ? > I can't do much with it right now, because I don't have any devices > that can do SMP idle with a v3.2 kernel. I've started working on an > updated version that avoids the spinlock, but it might be a while > before I can test and post it. I'm mostly looking for feedback on the > approach taken in this patch, and whether it will be useful for other > SoCs besides Tegra and OMAP4. Hi Colin, I will be happy to test your patchset. Do you have a pointer to a more recent kernel ? >> Did you have the opportunity to measure the power consumption with and >> without this patchset ? > Power consumption will be very dependent on the specific SoC in > question. The most important factors are the power savings of the > independent cpuidle state (normally WFI) vs. the hotplug state > (normally 1 cpu in OFF), and the workload being tested. > > On a very idle system, these patches result in the same total power as > hotplugging one cpu and letting the other idle normally. On a 25% > busy system, you might see a slight increase in power, as the best > independent cpuidle state might be WFI, vs 1 cpu in OFF mode in > hotplug. On OMAP4, that difference is small, on the order of 10 mW. > Once you hit the threshold where a hotplug governor would have > hotplugged in the second cpu (lets say 40%), the savings from these > patches are enormous, as you can hit the lowest power state up to 60% > of the time, where the hotplug solution would never be going below WFI > on both cpus. On OMAP4, that can be well over 100 mW. Interesting. Thanks -- Daniel