From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752216Ab0CRV5f (ORCPT ); Thu, 18 Mar 2010 17:57:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60401 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751824Ab0CRV5e (ORCPT ); Thu, 18 Mar 2010 17:57:34 -0400 Message-ID: <4BA2A1CD.1070207@redhat.com> Date: Thu, 18 Mar 2010 17:57:33 -0400 From: William Cohen User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.8) Gecko/20100301 Fedora/3.0.3-1.fc12 Lightning/1.0b2pre Thunderbird/3.0.3 MIME-Version: 1.0 To: Linux Kernel Mailing List Subject: Re: [PATCH] Enhance perf to collect KVM guest os statistics fromhost side Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Ingo Molnar wrote: > * Avi Kivity wrote: > > > Monitoring guests from the host is useful for kvm developers, but less so > > for users. > > Guest space profiling is easy, and 'perf kvm' is not about that. (plain 'perf' > will work if a proper paravirt channel is opened to the host) > > I think you might have misunderstood the purpose and role of the 'perf kvm' > patch here? 'perf kvm' is aimed at KVM developers: it is them who improve KVM > code, not guest kernel users. > > Ingo The software performance events work fine in a KVM guest. Do the hardware performance events work in KVM guest environment? Last time I looked the results for the hardware counters were not sane. The values were seemingly random numbers. Something like the following. Performance counter stats for 'ls': 3.427434 task-clock-msecs # 0.046 CPUs 2 context-switches # 0.001 M/sec 0 CPU-migrations # 0.000 M/sec 218 page-faults # 0.064 M/sec 140737488355327 cycles # 41062056440.861 M/sec 68825777242116 instructions # 0.489 IPC 68825777242117 branches # 20080846849.893 M/sec 68825777242118 branch-misses # 100.000 % cache-references cache-misses The guest image is using 2.6.34-0.10.rc1.git0.fc14.it68 kernel and the host is Fedora-12 with a kernel built from 2.6.34-rc1-tip+ git tree running on Quad-Core AMD Opteron(tm) Processor 2350. Is there some combination of kernel/distribution/hardware that the hardware performance counters are suppose to work on? -Will