From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1427919AbcBSPyE (ORCPT ); Fri, 19 Feb 2016 10:54:04 -0500 Received: from mail-wm0-f53.google.com ([74.125.82.53]:37521 "EHLO mail-wm0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751466AbcBSPx5 (ORCPT ); Fri, 19 Feb 2016 10:53:57 -0500 Subject: Re: [PATCH 4/4] KVM: x86: track actual TSC frequency from the timekeeper struct To: Marcelo Tosatti , KVM list , "linux-kernel@vger.kernel.org" References: <1454944711-33022-1-git-send-email-pbonzini@redhat.com> <1454944711-33022-5-git-send-email-pbonzini@redhat.com> <20160216134816.GA21944@amt.cnet> <20160216142544.GA23955@amt.cnet> <56C3558D.2020008@redhat.com> <20160219141203.GC3956@amt.cnet> From: Paolo Bonzini X-Enigmail-Draft-Status: N1110 Message-ID: <56C73A86.8040309@redhat.com> Date: Fri, 19 Feb 2016 16:53:42 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <20160219141203.GC3956@amt.cnet> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/02/2016 15:12, Marcelo Tosatti wrote: > >> > I need to check how often the timekeeper updates the parameters. > I'd assume once every tick, the function is called (the notifier). > > But you can optimize that away by only updating the TSC frequency > when mult/shift are updated, which should be much rarer. Yes, exactly. That would still not be rate limiting. But worst case it can be a lot of adjustments, up to HZ per second... Paolo