Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755331Ab2EGDMs (ORCPT ); Sun, 6 May 2012 23:12:48 -0400 Received: from e23smtp08.au.ibm.com ([202.81.31.141]:57483 "EHLO e23smtp08.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755205Ab2EGDMr (ORCPT ); Sun, 6 May 2012 23:12:47 -0400 Message-ID: <4FA73A94.1090309@linux.vnet.ibm.com> Date: Mon, 07 May 2012 10:59:32 +0800 From: Michael Wang User-Agent: Mozilla/5.0 (X11; Linux i686; rv:11.0) Gecko/20120412 Thunderbird/11.0.1 MIME-Version: 1.0 To: Diwakar Tundlam CC: "'Michael Neuling'" , "'Peter Zijlstra'" , "'Ingo Molnar'" , "'Andrew Morton'" , "'Christoph Lameter'" , "'Stephen Rothwell'" , "'Benjamin Herrenschmidt'" , "'David Rientjes'" , "'linux-kernel@vger.kernel.org'" , Peter De Schrijver Subject: Re: [PATCH] sched: Enable arch-specific asym packing option in sched domain References: <1DD7BFEDD3147247B1355BEFEFE46652379C3DF0FF@HQMAIL04.nvidia.com> <1DD7BFEDD3147247B1355BEFEFE46652379C3DF101@HQMAIL04.nvidia.com> <1336169422.16236.1.camel@twins> <1DD7BFEDD3147247B1355BEFEFE46652379C3DF102@HQMAIL04.nvidia.com> <1336170586.16236.11.camel@twins> <1DD7BFEDD3147247B1355BEFEFE46652379C3DF103@HQMAIL04.nvidia.com> <19500.1336173634@neuling.org> <1DD7BFEDD3147247B1355BEFEFE46652379C3DF104@HQMAIL04.nvidia.com> In-Reply-To: <1DD7BFEDD3147247B1355BEFEFE46652379C3DF104@HQMAIL04.nvidia.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit x-cbid: 12050616-5140-0000-0000-00000131431F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4226 Lines: 105 On 05/05/2012 07:25 AM, Diwakar Tundlam wrote: >>> Arrh, so it's not a performance issue but power savings.. that would this asymmetric packing a lot more appropriate to use. > > Yes, it is for power saving.. > > Could you suggest a way t use this flag without affecting Power7, then? > I was thinking to define a different weak arch_sd_package_asym_packing() in SD_CPU_INIT. > And the flag is set only for arch/arm/mach-tegra/tegra3. > SD_ASYM_PACKING will help to change the idle processor from higher id to lower, so if a lower id cpu thread is going to idle, we will move all the tasks of it's higher id sibling to him. I don't know how can this way cause power saving? Do you mean on this tegra3 arch, higher id smt will use more power than lower one? And could the SD_POWERSAVINGS_BALANCE do some help in your case? Regards, Michael Wang > Thanks, > --Diwakar. > > -----Original Message----- > From: Michael Neuling [mailto:mikey@neuling.org] > Sent: Friday, May 04, 2012 4:21 PM > To: Diwakar Tundlam > Cc: 'Peter Zijlstra'; 'Ingo Molnar'; 'Andrew Morton'; 'Christoph Lameter'; 'Stephen Rothwell'; 'Benjamin Herrenschmidt'; 'David Rientjes'; 'linux-kernel@vger.kernel.org'; Peter De Schrijver > Subject: Re: [PATCH] sched: Enable arch-specific asym packing option in sched domain > >> Thanks for clarifying the Power7. I see the point - package vs cpu's within a package. >> >> Yes, this is for Nvidia's ARM Quad-core Tegra CPU. It is a single >> package, organized flatly. To save power, we want cores to be loaded >> up in order from cpu0, 1, etc. The ASYM_PACKING flag seems to do >> exactly what we need if set in the domain flag. > > Arrh, so it's not a performance issue but power savings.. that would this asymmetric packing a lot more appropriate to use. > > Mikey > >> >> Thanks, >> --Diwakar. >> >> -----Original Message----- >> From: Peter Zijlstra [mailto:a.p.zijlstra@chello.nl] >> Sent: Friday, May 04, 2012 3:30 PM >> To: Diwakar Tundlam >> Cc: 'Ingo Molnar'; 'Andrew Morton'; 'Christoph Lameter'; 'Michael >> Neuling'; 'Stephen Rothwell'; 'Benjamin Herrenschmidt'; 'David >> Rientjes'; 'linux-kernel@vger.kernel.org'; Peter De Schrijver >> Subject: RE: [PATCH] sched: Enable arch-specific asym packing option >> in sched domain >> >> On Fri, 2012-05-04 at 15:18 -0700, Diwakar Tundlam wrote: >>> >>> arch_sd_sibling_asym_packing() is already present under ifdef CONFIG_SMT. >>> I didn't touch that. I only added it to SD_CPU_INIT for all cpu's. >>> I assumed Power7 shouldn't use SD_CPU_INIT. >> >> All archs use SD_CPU_INIT, its the default topology level for a package/socket. So now you've made Power7 prefer lower numbered sockets over higher numbered sockets.. not fatal, but not really nice either. >> >> [ power7 is the only one that implements arch_sd_sibling_asym_packing >> ] >> >>> Maybe I should define a separate weak symbol, say arch_sd_bias_to_lower_num_cpu()? >>> Then Power7 can define arch_sd_sibling_asym_packing() to be '1' and >>> it will not break all-cpu init. >> >> A slightly saner name would be: >> >> arch_sd_package_asym_packing() >> >> FWIW, I suspect you're wanting to use this for some ARM chip (nvidia >> doesn't do much else -- aside from this graphics stuff) so that if >> there's hardly anything it runs on cpu0. Now, last time I checked, >> these ARM things had only 1 package, so I still don't see the point >> :-) >> >> I suspect you want to modify SD_MC_INIT() with something like: >> >> arch_sd_mc_asym_packing() >> >> Or is this the big-little thing and you're representing them as separate packages? >> >> See how a little extra information avoids me having to endlessly second guess wtf you're actually wanting to do? >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/