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

[Jonathan Rajotte]

Hi,

On Aug 24, 2016 12:18 PM, "Francis Deslauriers" <francis.deslauriers at mail.
utoronto.ca> wrote:
>
> Hi David,
> If you specifically want to trace the scheduling of the threads of your
app, you don't need custom tracepoints.
> Enabling the sched_switch kernel event will give you both of cpu id and
thread id. Look at the cpu_id and next_tid fields.
>
> You can enable the sched_switch event using : lttng enable-event -k
sched_switch

In TraceCompass you can inspect this data with the control flow view and
the Ressource view under the Kernel analysis node under the trace node in
the project explorer.

I'm not sure of the base requirement for those views you can use the safe
enable-event:

lttng enable-event -k 'sched*'


You can also use "lttng track" to limi the gathering of event to a certain
pid.


Another way to reduce the scope would be to filter per procname:


lttng create
lttng add-context -k -t procname
lttng enable-event 'sched*' --filter '$ctx.procname == "PROCNAMEHERE"'

>
> Cheers,
> Francis
>
>
> 2016-08-24 3:17 GMT-04:00 David Aldrich <David.Aldrich at emea.nec.com>:
>>
>> Hi
>>
>>
>>
>> I am new to tracing in Linux and to lttng. I have a multi-threaded user
application and I want to see:
>>
>>
>>
>> 1)      When the threads are scheduled to run
>>
>> 2)      Which cores the threads are running on.
>>
>>
>>
>> I have installed lttng on Ubuntu 14.04 LTS.  I am expecting to visualise
the trace using TraceCompass.
>>
>>
>>
>> I have read the following doc section:
>>
>>
>>
>> http://lttng.org/docs/#doc-tracing-your-own-user-application
>>
>>
>>
>> In order to collect my trace, must I define custom tracepoint
definitions ( in a tracepoint provider header file ), and insert
tracepoints into my user application, or is there a simpler way of
achieving my goal?
>>
>>
>>
>> Best regards
>>
>>
>>
>> David
>>
>>
>>
>>
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>>
>
>
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