From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751374AbcGLFCw (ORCPT ); Tue, 12 Jul 2016 01:02:52 -0400 Received: from hr2.samba.org ([144.76.82.148]:20976 "EHLO hr2.samba.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750853AbcGLFCu (ORCPT ); Tue, 12 Jul 2016 01:02:50 -0400 X-Greylist: delayed 1492 seconds by postgrey-1.27 at vger.kernel.org; Tue, 12 Jul 2016 01:02:50 EDT Date: Tue, 12 Jul 2016 14:37:45 +1000 From: Anton Blanchard To: Thomas Gleixner Cc: LKML , Peter Zijlstra , Ingo Molnar , rt@linutronix.de, Michael Ellerman , Vaidyanathan Srinivasan , shreyas@linux.vnet.ibm.com Subject: Re: [patch 10/15] sched/migration: Move calc_load_migrate() into CPU_DYING Message-ID: <20160712143745.430733e7@kryten> In-Reply-To: <20160310120025.328739226@linutronix.de> References: <20160310115406.940706476@linutronix.de> <20160310120025.328739226@linutronix.de> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Thomas, > It really does not matter when we fold the load for the outgoing cpu. > It's almost dead anyway, so there is no harm if we fail to fold the > few microseconds which are required for going fully away. We are seeing the load average shoot up when hot unplugging CPUs (+1 for every CPU we offline) on ppc64. This reproduces on bare metal as well as inside a KVM guest. A bisect points at this commit. As an example, a completely idle box with 128 CPUS and 112 hot unplugged: # uptime 04:35:30 up 1:23, 2 users, load average: 112.43, 122.94, 125.54 Anton