linux-kernel - Re: [PATCH] KVM: VMX: add tracepoint for vpids

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Message-ID: <4F5F1D0D.8080408@redhat.com>
Date:	Tue, 13 Mar 2012 12:10:21 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Davidlohr Bueso <dave@....org>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	lkml <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH] KVM: VMX: add tracepoint for vpids

On 03/13/2012 12:58 PM, Davidlohr Bueso wrote:
> 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 <dave@....org>
> > > > >
> > > > > 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.

So it seems.  Tracepoints should be useful for production deployments,
not development.

-- 
error compiling committee.c: too many arguments to function

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