Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756249Ab1BIDh1 (ORCPT ); Tue, 8 Feb 2011 22:37:27 -0500 Received: from mailout-de.gmx.net ([213.165.64.23]:35253 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1756205Ab1BIDh0 (ORCPT ); Tue, 8 Feb 2011 22:37:26 -0500 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1905F1Irg506MsOmFSrNFZ/DNqPHMGMaenZ/V+CGa fXv4xyMti3HMsQ Subject: Re: [PATCH 3/3] sched: newidle balance set idle_timestamp only on successful pull From: Mike Galbraith To: Venkatesh Pallipadi Cc: Suresh Siddha , Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, Paul Turner , Nick Piggin In-Reply-To: <1297188819-19999-4-git-send-email-venki@google.com> References: <1297188819-19999-4-git-send-email-venki@google.com> Content-Type: text/plain; charset="UTF-8" Date: Wed, 09 Feb 2011 04:37:21 +0100 Message-ID: <1297222641.8035.4.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.30.1.2 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 957 Lines: 26 On Tue, 2011-02-08 at 10:13 -0800, Venkatesh Pallipadi wrote: > load_balance() could return a negative value in the case of > SMT sibling CPU being busy. Code in idle_balance() though, uses this > return value as an indicator of successful task pull, ignoring the > -1 return value. Yup, garden variety bug. > This has two problems: > 1) Resets idle_stamp even when this return value is -1. > Specific case is on SMT capable system, CPU A is idle and its sibling > CPU B is busy. In this case, CPU A avg_idle will not depend on > a task sleeping/waking up on it. Instead it will continue to hold stale > avg_idle value for extended period of time. Not good. Acked-by: Mike Galbraith -Mike -- 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/