From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751921AbaFJMYm (ORCPT ); Tue, 10 Jun 2014 08:24:42 -0400 Received: from casper.infradead.org ([85.118.1.10]:49195 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750993AbaFJMYk (ORCPT ); Tue, 10 Jun 2014 08:24:40 -0400 Date: Tue, 10 Jun 2014 14:24:35 +0200 From: Peter Zijlstra To: Morten Rasmussen Cc: Henrik Austad , "linux-kernel@vger.kernel.org" , "linux-pm@vger.kernel.org" , "mingo@kernel.org" , "rjw@rjwysocki.net" , "vincent.guittot@linaro.org" , "daniel.lezcano@linaro.org" , "preeti@linux.vnet.ibm.com" , Dietmar Eggemann Subject: Re: [RFC PATCH 02/16] sched: Introduce CONFIG_SCHED_ENERGY Message-ID: <20140610122435.GG6758@twins.programming.kicks-ass.net> References: <1400869003-27769-1-git-send-email-morten.rasmussen@arm.com> <1400869003-27769-3-git-send-email-morten.rasmussen@arm.com> <20140608060316.GA18179@austad.us> <20140609102027.GA29593@e103034-lin> <20140610093943.GA6758@twins.programming.kicks-ass.net> <20140610100641.GB1581@e103034-lin> <20140610102353.GC6758@twins.programming.kicks-ass.net> <20140610112403.GC1581@e103034-lin> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="gJgGjUUWrnN4mpen" Content-Disposition: inline In-Reply-To: <20140610112403.GC1581@e103034-lin> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --gJgGjUUWrnN4mpen Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jun 10, 2014 at 12:24:03PM +0100, Morten Rasmussen wrote: > On Tue, Jun 10, 2014 at 11:23:53AM +0100, Peter Zijlstra wrote: > > On Tue, Jun 10, 2014 at 11:06:41AM +0100, Morten Rasmussen wrote: > > > How would you like to disable the energy stuff for users for whom > > > latency is everything? > > >=20 > > > I mean, we are adding some extra load/utilization tracking. While I > > > think we should do everything possible to minimize the overhead, I th= ink > > > it is unrealistic to assume that it will be zero. Is a some extra 'if > > > (energy_enabled)' acceptable? > > >=20 > > > I'm open for other suggestions. > >=20 > > We have the jump-label stuff to do self modifying code ;-) The only > > thing we need to be careful with is data-layout. >=20 > Thanks. I can see that it is already used in for various bit in > kernel/sched/*. I didn't catch anything in Documentation/static-keys.txt > related to data-layout caveats. Is there some other > documentation/patches I should read before messing everything up? ;-) So the data-layout was mostly referring to things like making sure that struct sched_avg doesn't end up straddling a cacheline somewhere by accident. The most expensive part of the per-task accounting nonsense is the amount of memory we need to touch to do so, the actual instructions come second, unless of course we go put tons of divisions in there :-) BTW, are cachelines 64 bytes for you ARM people too? --gJgGjUUWrnN4mpen Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJTlvkDAAoJEHZH4aRLwOS65qQP/RkQjZTvnviSG5PwG4lCiBgk W53tNIdEKmkqpX/Nv0jomq0JGrd+GaVifrj1iNxXJVZ7ZnLR8lGdJvbL59Kxesl2 5mW6SyWXHil4M8ILHRDTWqtMsQVo6oMNTUYj+TfU6h1rsNk7kZDNL0tVTH/jsXTX uK6Q/zUz4BH3R+ohxOULbl15J+/YUFgVKi8e3R+07vHrh8M1ig+eBh4FtTZpBjVT J1Jgh3OxOraz3RQh1g0EC6vg04lw1QDOCMvy5DGGR8ZXYOsVEekDznzSosbLO19e j0aqMt2VPwZBqQKrj+xsg160cWbUPK+3pjIBRi5ZAu5wvpqJW7vZL3cXFgundU8d bFLFWh20aw0hOep2MTeVjbt8wlcJOUgyct7lFm4GP75iHWT6hB9AxaFEH+yjfrPP nzTnKH558n31Xgg8uHOvaQCjDZ0L+vmypuVP3CKVYaTBwpHLiWyKfJM9/OkW+kd8 rM8sxDJW/BB62c1cFaV1gee7wFbYYVBWSwitA0FnSfgiRn2XBJgCNJ1DV6/5yKw5 f6ifI3js93grHRkEWU3T04RFlMTKtoD1ABl2Y1MVAj+sr9oiqSdHi5l4iuZYkRbI IB+QBZqNMx+P9yptZC9MU2Uuxh/cYpRtYTdQ4sCg2pkNRb8fcHiRWAR+GLmK4Sp7 vt4GOOBI02Kt/8WjAzbH =YZNU -----END PGP SIGNATURE----- --gJgGjUUWrnN4mpen--