From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTP id 2B2354C6 for ; Wed, 7 May 2014 21:03:49 +0000 (UTC) Received: from mail.windriver.com (mail.windriver.com [147.11.1.11]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id ABD7620279 for ; Wed, 7 May 2014 21:03:48 +0000 (UTC) Message-ID: <536A9FA9.3030705@windriver.com> Date: Wed, 7 May 2014 17:03:37 -0400 From: Paul Gortmaker MIME-Version: 1.0 To: "Rafael J. Wysocki" , References: <1998761.B2k0A5OtQR@vostro.rjw.lan> In-Reply-To: <1998761.B2k0A5OtQR@vostro.rjw.lan> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: Peter Zijlstra , Len Brown , Daniel Lezcano , Ingo Molnar Subject: Re: [Ksummit-discuss] [TECH(CORE?) TOPIC] Energy conservation bias interfaces List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 14-05-06 08:54 AM, Rafael J. Wysocki wrote: > Hi All, > > During a recent discussion on linux-pm/LKML regarding the integration of the > scheduler with cpuidle (http://marc.info/?t=139834240600003&r=1&w=4) it became > apparent that the kernel might benefit from adding interfaces to let it know > how far it should go with saving energy, possibly at the expense of performance. These links from last year might be of general interest: http://lwn.net/Articles/571414/ http://etherpad.osuosl.org/energy-aware-scheduling-ks-2013 Paul. -- > > First of all, it would be good to have a place where subsystems and device > drivers can go and check what the current "energy conservation bias" is in > case they need to make a decision between delivering more performance and > using less energy. Second, it would be good to provide user space with > a means to tell the kernel whether it should care more about performance or > energy. Finally, it would be good to be able to adjust the overall "energy > conservation bias" automatically in response to certain "power" events such > as "battery is low/critical" etc. > > It doesn't seem to be clear currently what level and scope of such interfaces > is appropriate and where to place them. Would a global knob be useful? Or > should they be per-subsystem, per-driver, per-task, per-cgroup etc? > > It also is not particularly clear what representation of "energy conservation > bias" would be most useful. Should that be a number or a set of well-defined > discrete levels that can be given names (like "max performance", "high > prerformance", "balanced" etc.)? If a number, then what units to use and > how many different values to take into account? > > The people involved in the scheduler/cpuidle discussion mentioned above were: > * Amit Kucheria > * Ingo Molnar > * Daniel Lezcano > * Morten Rasmussen > * Peter Zijlstra > and me, but I think that this topic may be interesting to others too (especially > to Len who proposed a global "enefgy conservation bias" interface a few years ago). > > Please let me know what you think. > > Kind regards, > Rafael > > _______________________________________________ > Ksummit-discuss mailing list > Ksummit-discuss@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/ksummit-discuss >