From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755860Ab3GKJxp (ORCPT ); Thu, 11 Jul 2013 05:53:45 -0400 Received: from merlin.infradead.org ([205.233.59.134]:39912 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751478Ab3GKJxo (ORCPT ); Thu, 11 Jul 2013 05:53:44 -0400 Date: Thu, 11 Jul 2013 11:52:49 +0200 From: Peter Zijlstra To: Marcelo Tosatti Cc: mingo@redhat.com, gleb@redhat.com, glommer@parallels.com, tglx@linutronix.de, jeremy@goop.org, rostedt@goodmis.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] remove sched notifier for cross-cpu migrations Message-ID: <20130711095249.GA25631@dyad.programming.kicks-ass.net> References: <20130710103440.GO25631@dyad.programming.kicks-ass.net> <20130711012157.GA21489@amt.cnet> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130711012157.GA21489@amt.cnet> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 10, 2013 at 10:21:57PM -0300, Marcelo Tosatti wrote: > > Linux as a guest on KVM hypervisor, the only user of the pvclock > vsyscall interface, does not require notification on task migration > because: > > 1. cpu ID number maps 1:1 to per-CPU pvclock time info. > 2. per-CPU pvclock time info is updated if the > underlying CPU changes. > 3. that version is increased whenever underlying CPU > changes. > > Which is sufficient to guarantee nanoseconds counter > is calculated properly. > > Signed-off-by: Marcelo Tosatti Awesome, thanks! Acked-by: Peter Zijlstra