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Date: Thu, 24 Mar 2016 09:02:08 -0400
From: Luiz Capitulino <lcapitulino@redhat.com>
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Subject: Re: [Qemu-devel] [RFC] host and guest kernel trace merging
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To: Peter Xu <peterx@redhat.com>
Cc: kvm@vger.kernel.org, Stefan Hajnoczi <stefanha@gmail.com>, yoshihiro.yunomae.ez@hitachi.com, mtosatti@redhat.com, qemu-devel@nongnu.org, Steven Rostedt <rostedt@goodmis.org>, linux-trace-users@vger.kernel.org, stefanha@redhat.com, pbonzini@redhat.com

On Thu, 24 Mar 2016 13:16:20 +0800
Peter Xu <peterx@redhat.com> wrote:

> Hi, Steven,
> 
> On Fri, Mar 04, 2016 at 08:23:11AM -0500, Steven Rostedt wrote:
> > My idea for a trace-cmd server, is to have a --client operation, for
> > running on the guest.
> > 
> >  trace-cmd server --client <connection>
> > 
> > The connection will be some socket, either network or something
> > directly attached to the host.
> > 
> > Then on the host, we can have
> > 
> >   trace-cmd server --connect <guest>
> > 
> > Where the server will create a connection to the guest.
> > 
> > And then, you could run on the host:
> > 
> >   trace-cmd record <host-events> --connect <guest> <guest-events>
> > 
> > And this will start recording host events, and then connect to the
> > local server that connects to the guest(s) and that will start tracing
> > on the guest as well.
> > 
> > Then events on the guest will be passed to the host server.
> > 
> > Something like this is my idea. We can work out the details on the best
> > way to get things working. We may be able to eliminate the host server
> > middle man. But I envision that we need a trace-cmd server running on
> > the guest to start off the commands.
> 
> Not sure whether fully I understand the above, it seems that we can
> remove the host server middle man (as you have mentioned). Moreover,
> I am not sure whether we can use this for multiple hosts as well,

Honest question, what's the multiple hosts use-case?

I would start by thinking about the most simple use-case: a host
and a guest with a single vCPU. Then add vCPUs, and then add multiple
guests.