From mboxrd@z Thu Jan 1 00:00:00 1970 From: Davidlohr Bueso Subject: Re: [PATCH] KVM: VMX: add tracepoint for vpids Date: Tue, 13 Mar 2012 11:58:05 +0100 Message-ID: <1331636285.12394.4.camel@offworld> References: <1331481472.17316.1.camel@offbook> <4F5DB245.9060205@redhat.com> <1331551781.1334.3.camel@offworld> <4F5DD140.7040605@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7BIT Cc: Marcelo Tosatti , lkml , KVM To: Avi Kivity Return-path: In-reply-to: <4F5DD140.7040605@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Mon, 2012-03-12 at 12:34 +0200, Avi Kivity wrote: > On 03/12/2012 01:29 PM, Davidlohr Bueso wrote: > > On Mon, 2012-03-12 at 10:22 +0200, Avi Kivity wrote: > > > On 03/11/2012 05:57 PM, Davidlohr Bueso wrote: > > > > From: Davidlohr Bueso > > > > > > > > Add a new tracepoint for vpid allocation and freeing associated to all vCPUs. > > > > > > > > > > Why? > > > > > > > We have been using this tracepoint for some time now to help debug vpids > > and simulating tagged TLB behavior and performance. This gets to be non > > trivial when working with large amounts of guests and vCPUs. > > I don't follow. Can you give an example of when this tracepoint would > be useful? > For example when running lots of guests with many different hardware configurations (ept on/off, vpid on/off) I trace what vcpu has or doesn't have a corresponding vpid associated. Perhaps this is more useful for experimental things than actual KVM development.