From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932436Ab1KQPzl (ORCPT ); Thu, 17 Nov 2011 10:55:41 -0500 Received: from casper.infradead.org ([85.118.1.10]:57756 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932312Ab1KQPzl (ORCPT ); Thu, 17 Nov 2011 10:55:41 -0500 Subject: Re: sched: Avoid SMT siblings in select_idle_sibling() if possible From: Peter Zijlstra To: Mike Galbraith Cc: Suresh Siddha , linux-kernel , Ingo Molnar , Paul Turner In-Reply-To: <1321544313.6308.25.camel@marge.simson.net> References: <1321350377.1421.55.camel@twins> <1321406062.16760.60.camel@sbsiddha-desk.sc.intel.com> <1321435455.5072.64.camel@marge.simson.net> <1321468646.11680.2.camel@sbsiddha-desk.sc.intel.com> <1321495153.5100.7.camel@marge.simson.net> <1321544313.6308.25.camel@marge.simson.net> Content-Type: text/plain; charset="UTF-8" Date: Thu, 17 Nov 2011 16:56:16 +0100 Message-ID: <1321545376.2495.1.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2011-11-17 at 16:38 +0100, Mike Galbraith wrote: > On Thu, 2011-11-17 at 02:59 +0100, Mike Galbraith wrote: > > On Wed, 2011-11-16 at 10:37 -0800, Suresh Siddha wrote: > > > > It should be ok. Isn't it? > > > > Nope, wasn't ok. > > Because you can't get to again: with a single E5620 package, it having > only SIBLING and MC domains. > > again: > for_each_domain(target, sd) { > if (!smt && (sd->flags & SD_SHARE_CPUPOWER)) > continue; > > if (!(sd->flags & SD_SHARE_PKG_RESOURCES)) { > if (!smt) { > smt = 1; > goto again; > D'0h, indeed.. Something like the below maybe, although I'm certain it all can be written much nicer indeed. --- kernel/sched/fair.c | 14 ++++++++------ 1 files changed, 8 insertions(+), 6 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index cd3b642..340e62e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2676,13 +2676,11 @@ static int select_idle_sibling(struct task_struct *p, int target) if (!smt && (sd->flags & SD_SHARE_CPUPOWER)) continue; - if (!(sd->flags & SD_SHARE_PKG_RESOURCES)) { - if (!smt) { - smt = 1; - goto again; - } + if (smt && !(sd->flags & SD_SHARE_CPUPOWER)) + break; + + if (!(sd->flags & SD_SHARE_PKG_RESOURCES)) break; - } sg = sd->groups; do { @@ -2702,6 +2700,10 @@ static int select_idle_sibling(struct task_struct *p, int target) sg = sg->next; } while (sg != sd->groups); } + if (!smt) { + smt = 1; + goto again; + } done: rcu_read_unlock();