Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753138Ab2FEV36 (ORCPT ); Tue, 5 Jun 2012 17:29:58 -0400 Received: from e2.ny.us.ibm.com ([32.97.182.142]:32839 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751231Ab2FEV34 (ORCPT ); Tue, 5 Jun 2012 17:29:56 -0400 Date: Tue, 5 Jun 2012 14:29:47 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: Thomas Gleixner , "Luck, Tony" , "Yu, Fenghua" , Rusty Russell , Ingo Molnar , H Peter Anvin , "Siddha, Suresh B" , "Mallick, Asit K" , Arjan Dan De Ven , linux-kernel , x86 , linux-pm , "Srivatsa S. Bhat" Subject: Re: [PATCH 0/6] x86/cpu hotplug: Wake up offline CPU via mwait or nmi Message-ID: <20120605212947.GA8686@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <87zk8iioam.fsf@rustcorp.com.au> <1338881971.28282.150.camel@twins> <3E5A0FA7E9CA944F9D5414FEC6C7122007727023@ORSMSX105.amr.corp.intel.com> <1338912565.2749.9.camel@twins> <3E5A0FA7E9CA944F9D5414FEC6C7122007728081@ORSMSX105.amr.corp.intel.com> <1338913190.2749.10.camel@twins> <3908561D78D1C84285E8C5FCA982C28F19300965@ORSMSX104.amr.corp.intel.com> <1338918625.2749.29.camel@twins> <1338925756.2749.36.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1338925756.2749.36.camel@twins> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12060521-5112-0000-0000-000008B4D7FF Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1585 Lines: 41 On Tue, Jun 05, 2012 at 09:49:16PM +0200, Peter Zijlstra wrote: > On Tue, 2012-06-05 at 21:43 +0200, Thomas Gleixner wrote: > > Vs. the interrupt/timer/other crap madness: > > > > - We really don't want to have an interrupt balancer in the kernel > > again, but we need a mechanism to prevent the user space balancer > > trainwreck from ruining the power saving party. > > What's wrong with having an interrupt balancer tied to the scheduler > which optimistically tries to avoid interrupting nohz/isolated/idle > cpus? Such an interrupt balancer would be a good thing, but I don't believe that it will be sufficient. > > - The timer issue is mostly solved by the existing nohz stuff > > (plus/minus the few bugs in there). > > Its not.. if you create an isolated domain there's no way to expel > existing timers from there. OK, I'll bite... Why not just use CPU hotplug to expel the timers? (Sorry, but you just can't expect me to pass that one up!) > > - The other details (silly IPIs) and cross CPU timer arming) are way > > easier to solve by a proper prohibitive state than by chasing that > > nonsense all over the tree forever. > > But we need to solve all that without a prohibitibe state anyway for the > isolation stuff to be useful. I bet that we will end up having to do both. Thanx, Paul -- 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/