Re: Multiple Tracers

Arnaldo Carvalho de Melo
2009-04-09T03:00:20Z

Em Thu, Apr 09, 2009 at 10:11:48AM +0800, Li Zefan escreveu:
> CC: Arnaldo Carvalho de Melo <acme@redhat.com>
>
> Ingo Molnar wrote:
> > * Steven Whitehouse <swhiteho@redhat.com> wrote:
> >
> >> Hi,
> >>
> >> On Wed, 2009-04-08 at 15:53 +0200, Ingo Molnar wrote:
> >>> * Steven Whitehouse <swhiteho@redhat.com> wrote:
> >>>
> >>>> Hi,
> >>>>
> >>>> A little while back I posted a RFC patch which added gfs2 glock
> >>>> tracing to blktrace. There was a suggestion that I should look
> >>>> instead at the generic tracing code and add a new tracer, but I've
> >>>> come up with a couple of issues along the way.
> >>>>
> >>>> I think from what I can see that its only possible to run a single
> >>>> tracer at once, so running blktrace (for example) would preclude
> >>>> me from also tracing gfs2's glocks at the same time. Also, I can
> >>>> see no mechanism by which I could ensure the sequencing between
> >>>> the blktrace and glock traces other than exporting the blktrace
> >>>> sequence number, even if running multiple tracers at the same time
> >>>> was possible.
> >>> There's a recent addition: the EVENT_TRACE() facility. Would that
> >>> suit your purposes?
> >>>
> >>> Ingo
> >> If I can get both blktrace and glock trace info from it, then yes.
> >> I thought that the blktrace output went either via the original
> >> relayfs path, or via its own tracer so that it wasn't possible to
> >> use it and the event trace facility at the same time, unless I use
> >> blktrace via relayfs. From what I've read I thought that probably
> >> the relayfs interface for blktrace might eventually be removed in
> >> favour of the generic tracing interface, but I'm not 100% sure of
> >> that, so perhaps someone can confirm the plans in that area?
> >
> > Tom Zanussi (Cc:-ed) recently converted the blktrace tracepoints to
>
> I guess you mean Arnaldo <acme@redhat.com> ;)

Nope, Tom:

Message-Id: <1235725261.8512.89.camel@charm-linux>

> > a tracing framework - and i think much of that could be reused to
> > add EVENT_TRACE() tracepoints to blktrace too.
> >
> > Tom, what's your take on this?
> >
> > In general, this is the direction we want to take: EVENT_TRACE()
> > tracepoints that can be used in a generic way, in any tracer.
> >
>
> Actually we've planed to do this, and for other tracers.

Yeah, being able to mix all kinds of tracers is the way to go.

- Arnaldo