Re: Multiple Tracers

[Ingo Molnar <mingo@elte.hu>]

* 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