Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752964AbbGBIGG (ORCPT ); Thu, 2 Jul 2015 04:06:06 -0400 Received: from mail-wg0-f45.google.com ([74.125.82.45]:33738 "EHLO mail-wg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752876AbbGBIFv (ORCPT ); Thu, 2 Jul 2015 04:05:51 -0400 Message-ID: <1435824347.5351.18.camel@gmail.com> Subject: Re: [PATCH?] Livelock in pick_next_task_fair() / idle_balance() From: Mike Galbraith To: Yuyang Du Cc: Peter Zijlstra , Rabin Vincent , "mingo@redhat.com" , "linux-kernel@vger.kernel.org" , Paul Turner , Ben Segall , Morten Rasmussen Date: Thu, 02 Jul 2015 10:05:47 +0200 In-Reply-To: <20150701232511.GA5197@intel.com> References: <20150630143057.GA31689@axis.com> <1435728995.9397.7.camel@gmail.com> <20150701145551.GA15690@axis.com> <20150701204404.GH25159@twins.programming.kicks-ass.net> <20150701232511.GA5197@intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 794 Lines: 18 On Thu, 2015-07-02 at 07:25 +0800, Yuyang Du wrote: > That being said, it is also obvious to prevent the livelock from happening: > idle pulling until the source rq's nr_running is 1, becuase otherwise we > just avoid idleness by making another idleness. Yeah, but that's just the symptom, not the disease. Better for the idle balance symptom may actually be to only pull one when idle balancing. After all, the immediate goal is to find something better to do than idle, not to achieve continual perfect (is the enemy of good) balance. -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/