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 5B682979 for ; Mon, 12 May 2014 20:59:12 +0000 (UTC) Received: from mezzanine.sirena.org.uk (mezzanine.sirena.org.uk [106.187.55.193]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id C0E8E201B3 for ; Mon, 12 May 2014 20:59:11 +0000 (UTC) Date: Mon, 12 May 2014 21:58:54 +0100 From: Mark Brown To: Amit Kucheria Message-ID: <20140512205854.GQ12304@sirena.org.uk> References: <1998761.B2k0A5OtQR@vostro.rjw.lan> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="yfIbrPjRokFEZXK3" Content-Disposition: inline In-Reply-To: Cc: Len Brown , ksummit-discuss@lists.linuxfoundation.org, Peter Zijlstra , 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: , --yfIbrPjRokFEZXK3 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Mon, May 12, 2014 at 05:23:11PM +0530, Amit Kucheria wrote: > On Tue, May 6, 2014 at 6:24 PM, Rafael J. Wysocki wrote: > > 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 > Drivers are always designed to go as fast as possible until there is > nothing to do and runtime PM kicks in. Do we really want drivers that > slow down file copy to the USB stick because we are on battery? Or > degrade audio/video quality to save power? The only usecase I can come > up with where this makes sense is the wifi connection where the driver > should perhaps throttle bitrates if the network isn't being used > actively. But that is a driver-internal decision. There's some tradeoffs around audio as well actually - typically there is a lot of room for degrading performance without much impact on real world users. That said of course hardware manufacturers are constantly working to eliminate the need for such tradeoffs so the longer we leave this stuff the less relevant it becomes. I'd guess this is fairly common for analogue circuits, a similar thing used to be the case with PMICs though for modern devices the need for explict tuning has been mostly eliminated and the hardware can do it autonomously (at least for the bits that burn most power). --yfIbrPjRokFEZXK3 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJTcTYLAAoJELSic+t+oim9GUMQAJbYBHBY1uH0VGkT1YL/8qFc jL8ApTbDrfskATGUs8u1TLK7e6m+TqsE2wF3oV9qiRtz53EXJNqSJCUdQAcnYg8L KY6K5eL9rRntiVrJR0QrE0tHj5ZlkviRA9SWzAA/JBdlKdbIBfPfFYt9gBvXGHdb jlstmXuQE1gMbz+2lMWGDStAU53RQtjV5SaEqCxi26BCXZwdF1NLHS381ZD/McVA X4O5vExemNmX29mftAlbLWZkdEob/fJ23p+a+2SbxwHYJqLbcG6S5iqtxjL90XdW fB9xvMZ548iaTABTAEa/OLSDuvmVsjMdENkZ6VJWROhKcuyT3FPro/jrtoIK+f9E ACNdim0moBnpkHICxA6sgohaBd3TrbcXltfkpyfu+53IgfYzw5+FES/IbJAS84Jh rcN7K1vONgysE1/6EMSI3gJyIe65ZK+e4ITJcgr2r+fIJ+snfSBP7EF7T1kDFsLY GAKRpQzIk78hpvFK+l9j/9TF3y+9kzQwiNrPTiPpr9voqlTTxWgyihUmsdrdQ3XP 3he5eQfFM2KrxHj2wBhqGOq4/LrEDSLFIY1dUpMMGcv/RS+6sq/s8KBAXmoY+O5G W7nXq98LXegd0dqBwa3RG7g74o4rGOIlyhNPaXXtfzepYPHh2sVDjqPUnzc1Fgjy OJ9eUcUy5TSh5Yen0Zjb =AeLL -----END PGP SIGNATURE----- --yfIbrPjRokFEZXK3--