From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751510AbdB0TI5 (ORCPT ); Mon, 27 Feb 2017 14:08:57 -0500 Received: from mx4-phx2.redhat.com ([209.132.183.25]:58052 "EHLO mx4-phx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751392AbdB0TIx (ORCPT ); Mon, 27 Feb 2017 14:08:53 -0500 Date: Mon, 27 Feb 2017 14:06:27 -0500 (EST) From: Paolo Bonzini To: Thomas Gleixner Cc: Peter Zijlstra , Wanpeng Li , Mike Galbraith , LKML , Ingo Molnar , Borislav Petkov Message-ID: <1104576579.26276825.1488222387110.JavaMail.zimbra@redhat.com> In-Reply-To: References: <1484811069.17751.14.camel@gmx.de> <20170227130440.GW6500@twins.programming.kicks-ass.net> <15367170-e1c0-8901-7e15-940d8d699c21@redhat.com> <20170227155954.GY6500@twins.programming.kicks-ass.net> <111f89b9-22e3-5a0f-3469-6f64092521ff@redhat.com> <20170227163606.GZ6500@twins.programming.kicks-ass.net> Subject: Re: tip.today - scheduler bam boom crash (cpu hotplug) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.4.164.1, 10.5.100.50] X-Mailer: Zimbra 8.0.6_GA_5922 (ZimbraWebClient - FF51 (Linux)/8.0.6_GA_5922) Thread-Topic: tip.today - scheduler bam boom crash (cpu hotplug) Thread-Index: oTop5YamdWCg/4yqdGKzNyrUhLsoGw== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- Original Message ----- > From: "Thomas Gleixner" > To: "Paolo Bonzini" > Cc: "Peter Zijlstra" , "Wanpeng Li" , "Mike Galbraith" , > "LKML" , "Ingo Molnar" , "Borislav Petkov" > Sent: Monday, February 27, 2017 6:40:46 PM > Subject: Re: tip.today - scheduler bam boom crash (cpu hotplug) > > On Mon, 27 Feb 2017, Paolo Bonzini wrote: > > diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c > > index 2724dc82f992..3080b6877190 100644 > > --- a/arch/x86/kernel/tsc.c > > +++ b/arch/x86/kernel/tsc.c > > @@ -1398,6 +1398,9 @@ void __init tsc_init(void) > > > > use_tsc_delay(); > > > > + if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC)) > > + mark_tsc_unstable("not invariant"); > > Errm, no. > > That makes TSC unusable for systems which do not go into C/P states in > which the TSC stops. There is a world outside KVM .... Actually I was surprised too by Peter's patch, as it was adding mark_tsc_unstable pretty much everywhere that didn't have nonstop TSC. But hopefully it would still be okay to call clear_sched_clock_stable in tsc_init, in the same way. Paolo