Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752410AbaGIGr6 (ORCPT ); Wed, 9 Jul 2014 02:47:58 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:42704 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751218AbaGIGr4 (ORCPT ); Wed, 9 Jul 2014 02:47:56 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v2.0.1 X-SHieldMailCheckerPolicyVersion: FJ-ISEC-20120718-3 Message-ID: <53BCE540.1010306@jp.fujitsu.com> Date: Wed, 9 Jul 2014 15:46:24 +0900 From: Yasuaki Ishimatsu User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Borislav Petkov CC: , , , , , , , , , Subject: Re: [PATCH] x86,cpu-hotplug: clear llc_shared_mask at CPU hotplug References: <53B3A991.2070502@jp.fujitsu.com> <20140702113253.GD1318@pd.tnic> <53B4E1A4.2050502@jp.fujitsu.com> <20140703095135.GA21776@pd.tnic> <53B5F201.5070804@jp.fujitsu.com> <20140704105913.GB9246@pd.tnic> In-Reply-To: <20140704105913.GB9246@pd.tnic> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-SecurityPolicyCheck-GC: OK by FENCE-Mail X-TM-AS-MML: No Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Borislav, Sorry for late reply and thank you for your explanation. I'm implementing your suggestion. After finishing test, I'll post a patch again. So when I post a patch, please review it. Thanks, Yasuaki Ishimatsu (2014/07/04 19:59), Borislav Petkov wrote: > On Fri, Jul 04, 2014 at 09:14:57AM +0900, Yasuaki Ishimatsu wrote: >> If so, why following maps are cleared by CPU offline? >> - cpu_sigling_map >> - cpu_core_map > > I'll let you figure that out on your own by doing some quality code > staring. Hint: search for usages outside of the CPU hotplug path. > > In any case, let me try to explain it to you one more time: if the core > numbers are static and don't change across physical hotplug, the cores > which share last level cache also remain the same. This is a static > property which doesn't simply change. > > For example, if cores 6-11 and 34-41 have been sharing the last level > cache, then if the node containing them gets unplugged and replugged > back again - then the same cores share that exact same cache and nothing > has changed. > > Except the core numbers, as you've shown. Which would be not only a > problem for the llc_shared_mask but also a big annoyance for sysadmins > and users having to realize that the topology enumeration has changed > and trying to make sense of what node went where and why isn't it the > same as when the machine booted. > > So what I'm trying to say is, we should keep the core numbering stable > across hotplug to avoid unnecessary confusion; the llc_shared_mask is > just a small issue which results from not doing that. > -- 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/