Messages in this thread | | | Date | Wed, 8 Apr 2009 16:24:13 +0200 | From | Ingo Molnar <> | Subject | Re: Multiple Tracers |
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* 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 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.
Ingo
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