Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755393Ab3C0IyR (ORCPT ); Wed, 27 Mar 2013 04:54:17 -0400 Received: from mail-bk0-f53.google.com ([209.85.214.53]:49905 "EHLO mail-bk0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753984Ab3C0IyL (ORCPT ); Wed, 27 Mar 2013 04:54:11 -0400 MIME-Version: 1.0 In-Reply-To: <1364373980.5053.57.camel@laptop> References: <1363955155-18382-1-git-send-email-vincent.guittot@linaro.org> <1363955155-18382-4-git-send-email-vincent.guittot@linaro.org> <1364301998.5053.17.camel@laptop> <5151BEF2.9090100@linux.intel.com> <1364373980.5053.57.camel@laptop> Date: Wed, 27 Mar 2013 09:54:09 +0100 Message-ID: Subject: Re: [RFC PATCH v3 3/6] sched: pack small tasks From: Vincent Guittot To: Peter Zijlstra Cc: Arjan van de Ven , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linaro-kernel@lists.linaro.org, mingo@kernel.org, linux@arm.linux.org.uk, pjt@google.com, santosh.shilimkar@ti.com, morten.rasmussen@arm.com, chander.kashyap@linaro.org, cmetcalf@tilera.com, tony.luck@intel.com, alex.shi@intel.com, preeti@linux.vnet.ibm.com, paulmck@linux.vnet.ibm.com, tglx@linutronix.de, len.brown@intel.com, amit.kucheria@linaro.org, corbet@lwn.net Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1388 Lines: 28 On 27 March 2013 09:46, Peter Zijlstra wrote: > On Tue, 2013-03-26 at 08:29 -0700, Arjan van de Ven wrote: >> > Isn't this basically related to picking the NO_HZ cpu; if the system >> > isn't fully symmetric with its power gates you want the NO_HZ cpu to be >> > the 'special' cpu. If it is symmetric we really don't care which core >> > is left 'running' and we can even select a new pack cpu from the idle >> > cores once the old one is fully utilized. >> >> you don't really care much sure, but there's some advantages for sorting "all the way left", >> e.g. to linux cpu 0. >> Some tasks only run there, and interrupts tend to be favored to that cpu as well on x86. > > Right, and I suspect all the big-little nonsense will have the little > cores on low numbers as well (is this architected or can a creative > licensee screw us over?) It's not mandatory to have little cores on low numbers even if it's advised > > So find_new_ilb() already does cpumask_first(), so it has a strong > leftmost preference. We just need to make sure it indeed does the right > thing and doesn't have some unintended side effect. > -- 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/