From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754569AbdEHOC3 (ORCPT ); Mon, 8 May 2017 10:02:29 -0400 Received: from vps0.lunn.ch ([178.209.37.122]:52826 "EHLO vps0.lunn.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750925AbdEHOC2 (ORCPT ); Mon, 8 May 2017 10:02:28 -0400 Date: Mon, 8 May 2017 16:02:25 +0200 From: Andrew Lunn To: Waldemar Rymarkiewicz Cc: Alan Cox , Florian Fainelli , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Network cooling device and how to control NIC speed on thermal condition Message-ID: <20170508140225.GD19995@lunn.ch> References: <20170425144501.0cfe27a5@lxorguk.ukuu.org.uk> <20170428115630.GG13231@lunn.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > However, the fact is that PHYs having active 1G/s link generate much > more heat than having 100M/s link independently from network traffic. Yes, this is true. I got an off-list email suggesting this power difference is very significant, more so than actually processing packets. > All cooling methods impact host only, but "net cooling" impacts remote > side in addition, which seems to me to be a problem sometimes. Also, > the moment of link renegotiation blocks rx/tx for upper layers, so the > user sees a pause when streaming a video for example. However, if a > system is under a thermal condition, does it really matter? I don't know the cooling subsystem too well. Can you express a 'cost' for making a change, as well as the likely result in making the change. You might want to make the cost high, so it is used as a last resort if other methods cannot give enough cooling. Andrew