Re: [PATCH] trace-cmd: rework of the pid detection of vcpus

[Steven Rostedt <rostedt@goodmis.org>]

On Tue, 24 May 2022 11:35:40 -0400
Vineeth Pillai <vineethrp@google.com> wrote:

> On Mon, May 23, 2022 at 9:47 AM Steven Rostedt <rostedt@goodmis.org> wrote:
> >  
> > > I think we should also think about versioning the guest/host protocols  
> >
> > We actually have that. We are currently at version 3. If this becomes too
> > much of an issue, we can always move to v4. But to do that would require a
> > lot more thinking, as I like to support all versions, and I don't want to
> > have a lot of them. Thus, if we need to update to v4. It would likely be a
> > entirely new protocol to fix and extend the issues of v3.
> >  
> Thanks for the details.. Yeah, doesn't make sense to have a version
> change for this.

But there may be other reasons to update to v4 ;-)

> 
> > > Sure, I will have a look at this again and see if/how we can fix this without
> > > touching existing protocol. I was thinking about adding the pid details to
> > > debugfs and then reading it from there. Its not optimal as we would need a
> > > supporting kernel, but it would be accurate if we have kernel support and we
> > > need not rely on trace messages to get the pids.  
> >
> > That would be useful too, in more than just trace-cmd I believe.
> >  
> Posted a patch upstream for exposing pid in debugfs:
> https://www.spinics.net/lists/kvm/msg278146.html

Saw that.

> 
> I shall work on trace-cmd changes as well once the above patch
> is finalized..

Thanks,

-- Steve