From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: Analysis of sched_mc_power_savings Date: Wed, 9 Jan 2008 14:20:14 +0100 Message-ID: <20080109132014.GF27196@elte.hu> References: <20080108173815.GA7793@dirshya.in.ibm.com> <20080108212400.GA8903@linux-os.sc.intel.com> <20080109111302.GC7793@dirshya.in.ibm.com> <20080109113507.GA29721@elte.hu> <20080109122847.GA28955@dirshya.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20080109122847.GA28955@dirshya.in.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: "Siddha, Suresh B" , discuss@LessWatts.org, Linux-pm mailing list , Linux Kernel List-Id: linux-pm@vger.kernel.org * Vaidyanathan Srinivasan wrote: > I will watch this during the experiments. I have been using klog > application to dump relayfs data. I did run powertop and top as well, > I will bind them to certain CPUs and isolate their impact. > > I believe the margin of error would be less since all the measurement > tasks sleep for long duration. ok, long duration ought to be enough. i think a possible explanation of your observtions would be this: sleepy workloads are affected more by the wakeup logic, and most of the power-savings works via runtime balancing. So perhaps try to add some SD_POWERSAVINGS_BALANCE logic to try_to_wake_up()? I think waking up on the same CPU where it went to sleep is the most power-efficient approach in general. (or always waking up where the wakee runs - this should be measured.) Right now try_to_wake_up() tries to spread out load opportunistically, which is throughput-maximizing but it's arguably not very power conscious. Ingo