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 12:54:50 -0700 Message-ID: <4D07CB8A.8060600@cisco.com> References: <901746004.680841292328577685.JavaMail.root@zmail07.collab.prod.int.phx2.redhat.com> <4D078D5A.9060804@codemonkey.ws> <4D07B0DB.7010701@cisco.com> <4D07CA3C.2010108@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Ulrich Obergfell , kvm@vger.kernel.org, glommer@redhat.com, zamsden@redhat.com, avi@redhat.com, mtosatti@redhat.com To: Anthony Liguori Return-path: Received: from sj-iport-6.cisco.com ([171.71.176.117]:51892 "EHLO sj-iport-6.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759844Ab0LNTyw (ORCPT ); Tue, 14 Dec 2010 14:54:52 -0500 In-Reply-To: <4D07CA3C.2010108@codemonkey.ws> Sender: kvm-owner@vger.kernel.org List-ID: On 12/14/10 12:49, Anthony Liguori wrote: > But that doesn't tell you what the impact is in real world workloads. > Before we start pushing all device emulation into the kernel, we need to > quantify how often gettimeofday() is really called in real workloads. The workload that inspired that example program at its current max load calls gtod upwards of 1000 times per second. The overhead of gettimeofday was the biggest factor when comparing performance to bare metal and esx. That's why I wrote the test program --- boils a complex product/program to a single system call. David > > Regards, > > Anthony Liguori > >> What's the relative speed of the in-kernel pmtimer compared to the PIT? >> >> David >> >