From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755524Ab2ETN7H (ORCPT ); Sun, 20 May 2012 09:59:07 -0400 Received: from e28smtp07.in.ibm.com ([122.248.162.7]:46806 "EHLO e28smtp07.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755500Ab2ETN7E (ORCPT ); Sun, 20 May 2012 09:59:04 -0400 Message-ID: <4FB8F86B.1080906@linux.vnet.ibm.com> Date: Sun, 20 May 2012 19:28:03 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120424 Thunderbird/12.0 MIME-Version: 1.0 To: Peter Zijlstra CC: "Srivatsa S. Bhat" , mingo@kernel.org, pjt@google.com, paul@paulmenage.org, akpm@linux-foundation.org, rjw@sisk.pl, nacc@us.ibm.com, rientjes@google.com, paulmck@linux.vnet.ibm.com, tglx@linutronix.de, seto.hidetoshi@jp.fujitsu.com, tj@kernel.org, mschmidt@redhat.com, berrange@redhat.com, nikunj@linux.vnet.ibm.com, vatsa@linux.vnet.ibm.com, liuj97@gmail.com, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH v5 0/5] CPU hotplug, cpusets, suspend/resume: Fixes, cleanups and optimizations References: <20120517165839.3011.98723.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20120517165839.3011.98723.stgit@srivatsabhat.in.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit x-cbid: 12052013-8878-0000-0000-000002846A38 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, Did you get a chance to take a look at this patchset? (I have added a summary of the changes between the versions below.) Thanks a lot! On 05/17/2012 10:29 PM, Srivatsa S. Bhat wrote: > Currently the kernel doesn't handle cpusets properly during suspend/resume. > After a resume, all non-root cpusets end up having only 1 cpu (the boot cpu), > causing massive performance degradation of workloads. One major user of cpusets > is libvirt, which means that after a suspend/hibernation cycle, all VMs > suddenly end up running terribly slow! > > Also, the kernel moves the tasks from one cpuset to another during CPU hotplug > in the suspend/resume path, leading to a task-management nightmare after > resume. > > Patch 1 fixes this by keeping cpusets unmodified in the suspend/resume path. > But to ensure we don't trip over, it keeps the sched domains updated during > every CPU hotplug in the s/r path. > This is a long standing issue and we need to fix up stable kernels too. > > The rest of the patches in the series are mostly cleanups/optimizations > (except patch 4 which is a non-critical bug fix). > Changelog: v5 : Don't do explicit save/restore of cpusets' cpu masks during s/r, to avoid the overhead of a new per-cpuset cpu mask to help with that. Also, ensure that the sched domains are updated on each hotplug. The s/r fix (patch 1) is now distinct from the cleanups (patches 2-5). v4 : (Never had this version. I skipped from v3 to v5 accidentally). v3 : Explicitly save and restore cpusets' cpu masks during s/r. Don't alter the semantics of regular cpu hotplug. http://thread.gmane.org/gmane.linux.kernel/1296339 v2 : http://thread.gmane.org/gmane.linux.documentation/4805/ v1 : thread.gmane.org/gmane.linux.kernel/1250097/ > -- > Srivatsa S. Bhat (5): > CPU hotplug, cpusets, suspend: Don't modify cpusets during suspend/resume > cpusets, hotplug: Implement cpuset tree traversal in a helper function > cpusets, hotplug: Restructure functions that are invoked during hotplug > cpusets: Update tasks' cpus_allowed mask upon updates to root cpuset > cpusets: Remove/update outdated comments > > > include/linux/cpuset.h | 4 + > kernel/cpuset.c | 161 +++++++++++++++++++++++++++++++++++------------- > kernel/sched/core.c | 44 +++++++++++-- > 3 files changed, 159 insertions(+), 50 deletions(-) Regards, Srivatsa S. Bhat