From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764860AbdJRKBZ (ORCPT ); Wed, 18 Oct 2017 06:01:25 -0400 Received: from mail.cn.fujitsu.com ([183.91.158.132]:41900 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1763300AbdJRKBU (ORCPT ); Wed, 18 Oct 2017 06:01:20 -0400 X-IronPort-AV: E=Sophos;i="5.43,368,1503331200"; d="scan'208";a="29346647" Subject: Re: [PATCH v6 1/4] sched/clock: interface to allow timestamps early in boot To: Pasha Tatashin , Thomas Gleixner , Peter Zijlstra References: <1504116205-355281-1-git-send-email-pasha.tatashin@oracle.com> <1504116205-355281-2-git-send-email-pasha.tatashin@oracle.com> <20170927125857.yvwefpejzskiduwu@hirez.programming.kicks-ass.net> <20170927131003.dxbvu7frcqgtiwaz@hirez.programming.kicks-ass.net> <4a62156c-ea0f-749f-e21b-37919dfda1df@cn.fujitsu.com> <20170927180548.GM17526@worktop.programming.kicks-ass.net> <20170927180950.GD439@worktop> <1dd60ace-c2aa-6c88-d4b0-cba934be4b79@cn.fujitsu.com> <20170928115814.hnpah2bgkuaegtct@hirez.programming.kicks-ass.net> <281ff50e-ea79-b006-57e9-e80a2728419b@oracle.com> <71796664-a804-4bdd-ecd6-9eba9ef8a968@cn.fujitsu.com> CC: , , , , , , , , From: Dou Liyang Message-ID: Date: Wed, 18 Oct 2017 18:01:16 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <71796664-a804-4bdd-ecd6-9eba9ef8a968@cn.fujitsu.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.167.226.106] X-yoursite-MailScanner-ID: 4AB1848029CE.AB8FA X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: douly.fnst@cn.fujitsu.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Pasha, Sorry to reply you so late. I have test the TSC sync in our machine with DR(Dynamic Reconfiguration) Linux kernel: Linux-4.14.0-rc5 NUMA nodes: 4 node. Use clock_gettime() to reach nano-second accuracy. It is OK that we setup our reconfigurable with "tsc=unstable". Thanks, dou. At 09/29/2017 11:00 PM, Dou Liyang wrote: > Hi, Pasha > > At 09/28/2017 09:11 PM, Pasha Tatashin wrote: >>>>> It will be best if we can support TSC sync capability in x86, but >>>>> seems >>>>> is not easy. >>>> >>>> Sure, your hardware achieving sync would be best, but even if it does >>>> not, we can still use TSC. Using notsc simple because you fail to sync >>>> TSCs is quite crazy. >>>> >>>> The thing is, we need to support unsync'ed TSC in any case, because >>>> older chips (pre Nehalem) didn't have synchronized TSC in any case, and >>>> it still happens on recent chips if the BIOS mucks it up, which happens >>>> surprisingly often :-( >>>> >>>> I would suggest you try your reconfigurable setup with "tsc=unstable" >>>> and see if that works for you. That marks the TSC unconditionally >>>> unstable at boot and avoids any further wobbles once the TSC watchdog >>>> notices (although that too _should_ more or less work). >>> >>> That should do the trick nicely and we might just end up converting >>> notsc >>> to tsc=unstable silently so we can avoid the bike shed discussions about >>> removing it. >>> >> >> Ok, I will start working on converting notsc to unstable, and modify my >> patches to do what Peter suggested earlier. In the mean time, I'd like >> to hear from Dou if this setup works with dynamic reconfig. >> > > OK, I will do it, But, October 1 is our national holiday, I will in > holiday, and I just returned the test machine. :-( > > May reply you in middle of the October. > > Thanks, > > dou. > >> Thank you, >> Pasha >> >> >>