From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David S. Ahern" Subject: Re: [RFC 0/4] KVM in-kernel PM Timer implementation Date: Tue, 14 Dec 2010 11:00:59 -0700 Message-ID: <4D07B0DB.7010701@cisco.com> References: <901746004.680841292328577685.JavaMail.root@zmail07.collab.prod.int.phx2.redhat.com> <4D078D5A.9060804@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Anthony Liguori , kvm@vger.kernel.org, glommer@redhat.com, zamsden@redhat.com, avi@redhat.com, mtosatti@redhat.com To: Ulrich Obergfell Return-path: Received: from sj-iport-4.cisco.com ([171.68.10.86]:13351 "EHLO sj-iport-4.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751205Ab0LNSBB (ORCPT ); Tue, 14 Dec 2010 13:01:01 -0500 In-Reply-To: <4D078D5A.9060804@codemonkey.ws> Sender: kvm-owner@vger.kernel.org List-ID: On 12/14/10 08:29, Anthony Liguori wrote: >> I recently used to investigate the performance benefit. In a Linux >> guest, I was running a program that calls gettimeofday() 'n' times >> in a loop (the PM Timer register is read during each call). With >> in-kernel PM Timer, I observed a significant reduction of program >> execution time. >> > > I've played with this in the past. Can you post real numbers, > preferably, with a real work load? 2 years ago I posted relative comparisons of the time sources for older RHEL guests: http://www.mail-archive.com/kvm@vger.kernel.org/msg07231.html What's the relative speed of the in-kernel pmtimer compared to the PIT? David