From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751988AbaHRR1V (ORCPT ); Mon, 18 Aug 2014 13:27:21 -0400 Received: from e8.ny.us.ibm.com ([32.97.182.138]:33763 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751597AbaHRR1T (ORCPT ); Mon, 18 Aug 2014 13:27:19 -0400 Message-ID: <53F23761.6000904@linux.vnet.ibm.com> Date: Mon, 18 Aug 2014 22:56:57 +0530 From: Preeti U Murthy User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Nicolas Pitre CC: alex.shi@intel.com, vincent.guittot@linaro.org, peterz@infradead.org, pjt@google.com, efault@gmx.de, rjw@rjwysocki.net, morten.rasmussen@arm.com, svaidy@linux.vnet.ibm.com, arjan@linux.intel.com, mingo@kernel.org, len.brown@intel.com, yuyang.du@intel.com, linaro-kernel@lists.linaro.org, daniel.lezcano@linaro.org, corbet@lwn.net, catalin.marinas@arm.com, markgross@thegnar.org, sundar.iyer@intel.com, linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com, Lorenzo.Pieralisi@arm.com, mike.turquette@linaro.org, akpm@linux-foundation.org, paulmck@linux.vnet.ibm.com, tglx@linutronix.de Subject: Re: [RFC PATCH V2 01/19] sched/power: Remove cpu idle state selection and cpu frequency tuning References: <20140811113000.31956.52857.stgit@preeti.in.ibm.com> <20140811113145.31956.32224.stgit@preeti.in.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14081817-0320-0000-0000-000000413C0E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/18/2014 09:09 PM, Nicolas Pitre wrote: > On Mon, 11 Aug 2014, Preeti U Murthy wrote: > >> As a first step towards improving the power awareness of the scheduler, >> this patch enables a "dumb" state where all power management is turned off. >> Whatever additionally we put into the kernel for cpu power management must >> do better than this in terms of performance as well as powersavings. >> This will enable us to benchmark and optimize the power aware scheduler >> from scratch.If we are to benchmark it against the performance of the >> existing design, we will get sufficiently distracted by the performance >> numbers and get steered away from a sane design. > > I understand your goal here, but people *will* compare performance > between the old and the new design anyway. So I think it would be a > better approach to simply let the existing code be and create a new > scheduler-based governor that can be swapped with the existing ones at > run time. Eventually we'll want average users to test and compare this, > and asking them to recompile a second kernel and reboot between them > might get unwieldy to many people. > > And by allowing both to coexist at run time, we're making sure both the > old and the new code are built helping not breaking the old code. And > that will also cut down on the number of #ifdefs in many places. > > In other words, CONFIG_SCHED_POWER is needed to select the scheduler > based governor but it shouldn't force the existing code disabled. I don't think I understand you here. So are you proposing a runtime switch like a sysfs interface instead of a config switch? Wouldn't that be unwise given that its a complete turnaround of the behavior kernel after the switch? I agree that the first patch is a dummy patch, its meant to ensure that we have *atleast* the power efficiency that this patch brings in. Of course after that point this patch is a no-op. In fact the subsequent patches will mitigate the effect of this. Regards Preeti U Murthy > > >> Signed-off-by: Preeti U Murthy