From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: KVM PMU virtualization Date: Mon, 08 Mar 2010 12:15:17 +0200 Message-ID: <4B94CE35.2060408@redhat.com> References: <4B87987A.2020302@redhat.com> <20100226104437.GB7463@elte.hu> <4B87AF44.9090702@redhat.com> <20100226114217.GI7463@elte.hu> <4B87C354.9020209@redhat.com> <20100226130656.GA2518@elte.hu> <4B87CCF5.6000209@redhat.com> <20100226134400.GB23422@elte.hu> <20100228161142.GA19879@8bytes.org> <20100301084450.GF19395@elte.hu> <20100301111108.GE19879@8bytes.org> <1267463860.1579.25.camel@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Joerg Roedel , Ingo Molnar , Jes Sorensen , KVM General , Zachary Amsden , Gleb Natapov , ming.m.lin@intel.com, "Zhang, Yanmin" , Thomas Gleixner , "H. Peter Anvin" , Arjan van de Ven , Fr??d??ric Weisbecker , Arnaldo Carvalho de Melo To: Peter Zijlstra Return-path: Received: from mx1.redhat.com ([209.132.183.28]:52679 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753924Ab0CHKP6 (ORCPT ); Mon, 8 Mar 2010 05:15:58 -0500 In-Reply-To: <1267463860.1579.25.camel@laptop> Sender: kvm-owner@vger.kernel.org List-ID: On 03/01/2010 07:17 PM, Peter Zijlstra wrote: > > >> 2. For every emulated performance counter the guest activates kvm >> allocates a perf_event and configures it for the guest (we may allow >> kvm to specify the counter index, the guest would be able to use >> rdpmc unintercepted then). Event filtering is also done in this step. >> > rdpmc can never be used unintercepted, for perf might be multiplexing > the actual hw. > How often is rdpmc used? If it is invoked on high frequency software-only events (like context switches), then this may be a performance issue. If it is only issued on perf interrupts, we may be able to live with it (since we already took an exit for the interrupt). -- error compiling committee.c: too many arguments to function