From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752677Ab2DQQoP (ORCPT ); Tue, 17 Apr 2012 12:44:15 -0400 Received: from mga09.intel.com ([134.134.136.24]:52301 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751241Ab2DQQoO (ORCPT ); Tue, 17 Apr 2012 12:44:14 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,352,1309762800"; d="scan'208";a="130752802" Subject: Re: load balancing regression since commit 367456c7 From: Tim Chen To: Peter Zijlstra Cc: Suresh Siddha , Alex Shi , Ying , linux-kernel In-Reply-To: <1334664553.28150.87.camel@twins> References: <1334106376.19157.89.camel@schen9-DESK> <1334664553.28150.87.camel@twins> Content-Type: text/plain; charset="UTF-8" Date: Tue, 17 Apr 2012 09:44:14 -0700 Message-ID: <1334681054.3796.28.camel@schen9-DESK> Mime-Version: 1.0 X-Mailer: Evolution 2.32.3 (2.32.3-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-04-17 at 14:09 +0200, Peter Zijlstra wrote: > On Tue, 2012-04-10 at 18:06 -0700, Tim Chen wrote: > > |--56.52%-- load_balance > > | idle_balance > > | __schedule > > | schedule > > Ahh, I know why I didn't see it, I have a CONFIG_PREEMPT kernel and > idle_balancing stops once its gotten a single task over instead of > achieving proper balance. > > And since hackbench generates insanely long runqueues and the patch that > caused your regression 'fixed' the lock-breaking it will now iterate the > entire runqueue if needed to achieve balance, which hurts. > > I think the patch I send ought to work, let me try disabling > CONFIG_PREEMPT. > -- yes, CONFIG_PREEMPT is turned off on my side. With the patch that you sent, the slowed down went from a factor of 4 down to a factor 2. So the run time is now twice as long vs four time as long vs v3.3 kernel. Tim