[lttng-dev] Beginner question: how to inspect scheduling of multi-threaded user application?

[David Aldrich]

Hi Jonathan

Thanks for your reply. What is 'comm' in 'prev_comm'?

Best regards

David

> -----Original Message-----
> From: lttng-dev [mailto:lttng-dev-bounces at lists.lttng.org] On Behalf Of
> Jonathan Rajotte Julien
> Sent: 16 September 2016 18:37
> To: lttng-dev at lists.lttng.org
> Subject: Re: [lttng-dev] Beginner question: how to inspect scheduling of
> multi-threaded user application?
> 
> Hi
> 
> 
> On 2016-09-16 07:43 AM, David Aldrich wrote:
> > Hi
> >
> > I wonder if I might ask for some more guidance please?
> >
> > I now have lttng and Trace Compass running on Ubuntu.  I want to inspect
> the scheduling of threads in my user-space application.  So far, I have
> successfully captured a trace with the sched_switch event enabled:
> >
> > $ sudo lttng enable-event -k sched_switch
> >
> > This indeed shows my app's threads.  However, it also shows all the other
> threads in the system and does not show clearly (to my understanding)
> when the threads are scheduled / blocked.
> >
> > I would like some guidance on how to improve this tracing.
> >
> > 1) Would it be better if I defined my own “tracepoint providers” and then
> set trace events for when a thread wakes / blocks?
> 
> Could be a solution but you might want the built-in utility of lttng to filter
> out all noise first using the filtering feature.
> 
> e.g I'm interested in sched_switch event where chrome is involved
> 
> lttng create
> lttng enable-event --kernel "sched_switch" --filter 'prev_comm == "chrome*"
> || next_comm == "chrome*"'
> lttng start
> ....
> 
> Using TraceCompass you will be mainly interested in the Control Flow View
> and the Resource view (show per cpu timeline activity).
> 
> >
> > 2) How could I show which core a thread is running on?
> 
> The Resource view from TraceCompass should help here.
> 
> Cheers
> 
> >
> > Best regards
> >
> > David
> > _______________________________________________
> > lttng-dev mailing list
> > lttng-dev at lists.lttng.org
> > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> 
> --
> Jonathan R. Julien
> Efficios
> 
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