From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753900AbeEHCFA (ORCPT ); Mon, 7 May 2018 22:05:00 -0400 Received: from mail-wr0-f182.google.com ([209.85.128.182]:45278 "EHLO mail-wr0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751828AbeEHCE5 (ORCPT ); Mon, 7 May 2018 22:04:57 -0400 X-Google-Smtp-Source: AB8JxZp5ndw40MtIuXTCT43j+qlvsAlATSoLwXE8AtMM9NEh1Hq+3w2K4JMr1P3bGhGEBKVU46jN2g== Date: Tue, 8 May 2018 04:04:53 +0200 From: Daniel Lezcano To: Lina Iyer Cc: edubezval@gmail.com, rui.zhang@intel.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, Ram Chandrasekar Subject: Re: [PATCH] drivers: thermal: step_wise: add support for hysteresis Message-ID: <20180508020453.GH19313@mai> References: <20180507175408.2154-1-ilina@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180507175408.2154-1-ilina@codeaurora.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 07, 2018 at 11:54:08AM -0600, Lina Iyer wrote: > From: Ram Chandrasekar > > From: Ram Chandrasekar > > Step wise governor increases the mitigation level when the temperature > goes above a threshold and will decrease the mitigation when the > temperature falls below the threshold. If it were a case, where the > temperature hovers around a threshold, the mitigation will be applied > and removed at every iteration. This reaction to the temperature is > inefficient for performance. > > The use of hysteresis temperature could avoid this ping-pong of > mitigation by relaxing the mitigation to happen only when the > temperature goes below this lower hysteresis value. I don't disagree with this but the ping-pong around a temperature is usually avoided with a P-I-D computation which is implemented with the IPA governor. Wouldn't be more interesting to add the power numbers like some other platforms, so the IPA could be used? You will probably have better results with the IPA than changing the step-wise governor behavior (which may potentially impact other users). -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog