From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 6/6] don't compute pvclock adjustments if we trust the tsc Date: Tue, 27 Apr 2010 21:03:55 +0300 Message-ID: <4BD7270B.3030201@redhat.com> References: <1272303988-21929-1-git-send-email-glommer@redhat.com> <1272303988-21929-2-git-send-email-glommer@redhat.com> <1272303988-21929-3-git-send-email-glommer@redhat.com> <1272303988-21929-4-git-send-email-glommer@redhat.com> <1272303988-21929-5-git-send-email-glommer@redhat.com> <1272303988-21929-6-git-send-email-glommer@redhat.com> <1272303988-21929-7-git-send-email-glommer@redhat.com> <20100427134013.GE18410@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Glauber Costa , kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Marcelo Tosatti Return-path: Received: from mx1.redhat.com ([209.132.183.28]:46204 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756509Ab0D0SEA (ORCPT ); Tue, 27 Apr 2010 14:04:00 -0400 In-Reply-To: <20100427134013.GE18410@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: On 04/27/2010 04:40 PM, Marcelo Tosatti wrote: > On Mon, Apr 26, 2010 at 01:46:28PM -0400, Glauber Costa wrote: > >> If the HV told us we can fully trust the TSC, skip any >> correction >> >> > Please drop this. Its not certain what is the best method to reduce > contention on the global variable. Whatever it is, can be done later. > > The problem is lead time. If we (or the cpu vendors) fix this in the hypervisor/processors in a year, then we want existing guests to take advantage of it immediately. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.