Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754463Ab1DAIPd (ORCPT ); Fri, 1 Apr 2011 04:15:33 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:48534 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752719Ab1DAIPa (ORCPT ); Fri, 1 Apr 2011 04:15:30 -0400 Date: Fri, 1 Apr 2011 13:45:22 +0530 From: Dipankar Sarma To: Len Brown Cc: Peter Zijlstra , Vaidyanathan Srinivasan , Trinabh Gupta , arjan@linux.intel.com, Stephen Rothwell , suresh.b.siddha@intel.com, benh@kernel.crashing.org, venki@google.com, ak@linux.intel.com, linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com Subject: Re: cpuidle asymmetry (was Re: [RFC PATCH V4 5/5] cpuidle: cpuidle driver for apm) Message-ID: <20110401081522.GA22339@in.ibm.com> Reply-To: dipankar@in.ibm.com References: <20110322123336.28725.29810.stgit@tringupt.in.ibm.com> <20110323121458.ec7cdaf9.sfr@canb.auug.org.au> <4D89CA7D.8080108@linux.vnet.ibm.com> <4D8B550D.5000409@linux.vnet.ibm.com> <20110325180156.GC19214@dirshya.in.ibm.com> <1301577536.4859.249.camel@twins> 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) X-Content-Scanned: Fidelis XPS MAILER Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1343 Lines: 32 On Fri, Apr 01, 2011 at 12:09:25AM -0400, Len Brown wrote: > > > Moorestown is already an example of an asymmetric system, > > > since its deepest c-state is available on cpu0, but not on cpu1. > > > So it needs different tables for each cpu. > > > > wtf are these hardware guys smoking and how the heck are we supposed to > > schedule on such a machine? Prefer to keep cpu1 busy while idling cpu0? > > they are smoking micro-amps:-) > > S0i3 on cpu0 can be entered only after cpu1 is already off-line, > among other system hardware dependencies... > > So it makes no sense to export S0i3 as a c-state on cpu1. > > When cpu1 is online, the scheduler treats it as a normal SMP. Isn't S0i3 a "system" state, as opposed to cpu state ? Perhaps we can treat it as such and still keep the c-states symmetric. The cpu can transition to S0i3 from any cpu as long as others are offlined, no ? In that sense, really all the cpus would be in S0i3, which would make it symmetric. If this isn't how mrst cpuidle works, then cpuidle accounting may be broken in principle because of this. Thanks Dipankar -- 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/