From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752233AbbKIL55 (ORCPT ); Mon, 9 Nov 2015 06:57:57 -0500 Received: from fw-tnat.cambridge.arm.com ([217.140.96.140]:54210 "EHLO cam-smtp0.cambridge.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751815AbbKIL5z (ORCPT ); Mon, 9 Nov 2015 06:57:55 -0500 From: Punit Agrawal To: Jacob Pan Cc: Peter Zijlstra , Eduardo Valentin , Thomas Gleixner , LKML , Arjan van de Ven , Paul Turner , Len Brown , Srinivas Pandruvada , Tim Chen , Andi Kleen , Rafael Wysocki Subject: Re: [RFC PATCH 0/3] CFS idle injection References: <1446509428-5616-1-git-send-email-jacob.jun.pan@linux.intel.com> <20151104060654.GC8850@localhost.localdomain> <20151104085830.010e69f8@yairi> <20151105101218.GB3604@twins.programming.kicks-ass.net> <9hhvb9f843c.fsf@e105922-lin.cambridge.arm.com> <20151106111838.6172085d@icelake> Date: Mon, 09 Nov 2015 11:56:51 +0000 In-Reply-To: <20151106111838.6172085d@icelake> (Jacob Pan's message of "Fri, 6 Nov 2015 11:18:38 -0800") Message-ID: <9hhbnb38jy4.fsf@e105922-lin.cambridge.arm.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jacob Pan writes: > On Fri, 06 Nov 2015 16:50:15 +0000 > Punit Agrawal wrote: > >> * idle injection once frequencies have been capped to the lowest >> feasible values (as suggested in the cover letter) >> > actually, I was suggesting to start considering idle injection once > frequency capped to the energy efficient point, which can be much > higher than the lowest frequency. The idea being, deep idle power is > negligible compared to running power which allows near linear > power-perf scaling for balanced workload. > Below energy efficient frequency, continuous lowering frequency may > lose disproportion performance vs. power. i.e. worse than linear. > I agree. I was making that assumption that with the ability to inject idle states, there wouldn't be a need to expose the inefficient frequency states. Do you still see a reason to do that? >> One question about the implementation in these patches - should the >> implementation hook into pick_next_task in core instead of CFS? Higher >> priority tasks might get in the way of idle injection. > My take is that RT and throttling will never go well together since they > are conflicting in principle. I am not sure I follow. If RT (or other higher priority classes) can't be throttled then the CPUs are not able to contribute towards constraining power consumption and hence temperature. This is especially true in certain platforms where tasks belong to the RT class to maintain user experience, e.g., audio and video. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/