[lttng-dev] Problem with perf:thread in 2.5.0

[Evgeniy Ivanov]

Jonathan, sorry, I've copied wrong output, original command was with
perf:thread:cpu-cycles:

> lttng add-context -u -t vpid -t perf:thread:cpu-cycles -t
perf:thread:instructions -t perf:thread:cache-misses
Session auto-20140724-091524 created.
Traces will be written in
/export/home/eiva/lttng-traces/auto-20140724-091524
UST context vpid added to all channels
Error: perf:thread:cpu-cycles: UST invalid context
Error: perf:thread:instructions: UST invalid context
Error: perf:thread:cache-misses: UST invalid context
Warning: Some command(s) went wrong
UST event eiva_test:* created in channel channel0

> lttng --version
lttng (LTTng Trace Control) 2.5.0 - Fumisterie

Later I've tried cpu-cycles separately and then accidentally switched to
perf:cpu. Now everything started to work, but nothing changed since then.
Though didn't check if we still get zeroes on another machine.


On Thu, Jul 24, 2014 at 7:01 PM, Jonathan Rajotte-Julien <
jonathan.rajotte-julien at ericsson.com> wrote:

> Hi!
>
> > Hi!
> >
> > I use lttng-2.5.0 (tools, modules, …) and linux-3.8.13. When I try to
> add context for performance counters I get the following error:
> >
> >> lttng add-context -u -t perf:cpu:cpu-cycles
> > Error: perf:cpu:cpu-cycles: UST invalid context
> > Warning: Some command(s) went wrong
>
> Well i think we will both agree that the help page does not help very
> much.(Should fix that)
>
> If we go deep down into the code we get the supported context for UST
> domain. :)
>
> Ust domain support 6 type of context:
> LTTNG_EVENT_CONTEXT_VTID
> LTTNG_EVENT_CONTEXT_VPID
> LTTNG_UST_CONTEXT_VPID
> LTTNG_EVENT_CONTEXT_PTHREAD_ID
> LTTNG_EVENT_CONTEXT_PROCNAME
> LTTNG_EVENT_CONTEXT_IP
> LTTNG_EVENT_CONTEXT_PERF_THREAD_COUNTER
>
> Well this does help a little ... If we dig a little deeper and search
> around we get more info and see that an enum from
> "./lttng-tools/include/lttng/event.h" lttng_event_context_t maps to another
> one in the lttng-tool side ( context_type in add_context.c)
>
> *Important Part*
> So if we decrypt the macros and functions in add-context.c, we get that
> the following contexts are supported for UST:
>
> vpid
> vtid
> pthread_id
> procname
> ip
>
> perf:thread:cpu-cycles
> perf:thread:cycles
> perf:thread:stalled-cycles-frontend
> perf:thread:idle-cycles-frontend
> perf:thread:stalled-cycles-backend
> perf:thread:idle-cycles-backend
> perf:thread:instructions
> perf:thread:cache-references
> perf:thread:cache-misses
> perf:thread:branch-instructions
> perf:thread:branches
> perf:thread:branch-misses
> perf:thread:bus-cycles
>
> perf:thread:L1-dcache
> perf:thread:L1-icache
> perf:thread:LLC
> perf:thread:dTLB
> perf:thread:iTLB-loads
> perf:thread:iTLB-load-misses
> perf:thread:branch-loads
> perf:thread:branch-load-misses
>
> perf:thread:cpu-clock
> perf:thread:task-clock
> perf:thread:page-fault
> perf:thread:faults
> perf:thread:major-faults
> perf:thread:minor-faults
> perf:thread:context-switches
> perf:thread:cs
> perf:thread:cpu-migrations
> perf:thread:migrations
> perf:thread:alignment-faults
> perf:thread:emulation-faults
>
> **(TL;DR : perf:cpu:cpu-cycles is not in the list)**
>
> If you want perf:cpu:cpu-cycles you will need a kernel tracing domain.
>
> Even if it make sense that a ust tracing session cannot touch hardware
> stuff it won’t hurt to be more explicit about it. :).
>
> >
> > We have another machine with 2.5.0 (modules are not installed though)
> and adding perf:cpu:cpu-cycles works fine, but it is always zero in results.
>
> As for this, I cannot explain why lttng-tool does not complain on adding
> the context.
> You can open a bug here http://bugs.lttng.org/projects/lttng-tools (you
> will need to create an account and sign in)
>
> Cheers,
> Jonathan
>
> >
> > --
> > Cheers,
> > Evgeniy
> >
> >
> > _______________________________________________
> > lttng-dev mailing list
> > lttng-dev at lists.lttng.org
> > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> >
>
>


-- 
Cheers,
Evgeniy
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