From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753055AbbFAIOr (ORCPT ); Mon, 1 Jun 2015 04:14:47 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:51069 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932297AbbFAIOi (ORCPT ); Mon, 1 Jun 2015 04:14:38 -0400 Date: Mon, 1 Jun 2015 10:14:29 +0200 From: Peter Zijlstra To: Mike Galbraith Cc: LKML , Ingo Molnar , ktkhai@parallels.com Subject: Re: sched_setscheduler() vs idle_balance() race Message-ID: <20150601081429.GP19282@twins.programming.kicks-ass.net> References: <1432799032.3237.119.camel@gmail.com> <20150528135355.GK3644@twins.programming.kicks-ass.net> <1432824866.3237.198.camel@gmail.com> <20150528152456.GO3644@twins.programming.kicks-ass.net> <1432924227.8727.23.camel@gmail.com> <1432925336.8727.29.camel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1432925336.8727.29.camel@gmail.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 29, 2015 at 08:48:56PM +0200, Mike Galbraith wrote: > > P.S. intel_idle is not all that wonderful on this box. > > - 78.31% [kernel] [k] _raw_spin_lock ▒ > - _raw_spin_lock ▒ > - 94.91% tick_broadcast_oneshot_control ▒ Your DL980 G7 has E7-4800 parts in, right? Which if Wikipedia is correct, resolves to a Nehalem-EX. Now the NHM-EX has a fun 'feature' that for (some?) idle states the local timer stops, so we have to revert back to a global broadcast timer. Now go count the number of cpus on your box and then imagine a global spinlock, oh wait, you already found it ^ :-)