Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756790Ab1DAOD0 (ORCPT ); Fri, 1 Apr 2011 10:03:26 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:34522 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756620Ab1DAODZ convert rfc822-to-8bit (ORCPT ); Fri, 1 Apr 2011 10:03:25 -0400 Subject: Re: cpuidle asymmetry (was Re: [RFC PATCH V4 5/5] cpuidle: cpuidle driver for apm) From: Peter Zijlstra To: Len Brown Cc: 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 In-Reply-To: References: <20110322123208.28725.30945.stgit@tringupt.in.ibm.com> <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> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Fri, 01 Apr 2011 16:02:36 +0200 Message-ID: <1301666556.4859.695.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1104 Lines: 26 On Fri, 2011-04-01 at 00:09 -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:-) Has anybody told them that pushing lots of logic into software generally burns more amps because it keeps the thing running longer? > 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. Dipankar's reply seems to address this issue well. -- 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/