From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751422AbdLSSaS (ORCPT ); Tue, 19 Dec 2017 13:30:18 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:41636 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750798AbdLSSaO (ORCPT ); Tue, 19 Dec 2017 13:30:14 -0500 Subject: Re: [PATCH] arm64: defconfig: Select schedutil as default cpufreq governor To: Viresh Kumar , Catalin Marinas Cc: Vincent Guittot , arm@kernel.org, Will Deacon , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20171215155040.mlvd56i2rfgd2e2t@armageddon.cambridge.arm.com> <20171218042917.GB19815@vireshk-i7> From: Marc Zyngier Organization: ARM Ltd Message-ID: Date: Tue, 19 Dec 2017 18:30:11 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <20171218042917.GB19815@vireshk-i7> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18/12/17 04:29, Viresh Kumar wrote: > On 15-12-17, 15:50, Catalin Marinas wrote: >> On Thu, Nov 16, 2017 at 11:51:36AM +0530, Viresh Kumar wrote: >>> Currently performance governor is getting selected by default, which is >>> surely not a very good choice as its pretty much power hungry. >>> >>> Select schedutil instead. >> >> And why do we care about this in defconfig? People deploying their own >> kernels in mobile may opt for this config, others may prefer the default >> governor. >> >> Also it seems it would be the only architecture make this governor the >> default, so NAK. > > This is a bit dangerous configuration IMHO. > > Other architectures have some *real* governor selected by default, like Ondemand > or Conservative. Running your CPUs at max (because of the default performance > governor in arm64 config) may end up burning some SoCs accidentally just because > their thermal stuff doesn't kick in to cool SoC down properly. Honestly, this feels like widening a road because someone wants to drive a car with no steering wheel. If an SoC is broken enough not to to into thermal throttling on its own, I'm tempted to say "let it burn". And on-demand is just as bad as performance in that respect, as it will to the same thing as soon as you run (for example) Firefox. Or Emacs. > So, we should have one of ondemand, conservative and schedutil selected by > default for arm64 as well IMO and schedutil is the one which every one is > falling back to now a days, even android. I'll have my bike shed painted pink, thank you very much! :-) M. -- Jazz is not dead. It just smells funny...