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SubjectRe: Tracing of power:power_start events doesn't work
On Wed, May 05, 2010 at 08:34:17AM +0200, Ronny Tschüter wrote:
> On Wed 2010-05-05 02:31, Steven Rostedt wrote:
>> On Mon, 2010-05-03 at 15:19 +0200, Ronny Tschüter wrote:
>>
>>> Hello,
>>>
>>> i use kernel version 2.6.33.2 (x86-64, Core 2 Duo) and the perf events
>>> to track frequency and c states of my cpu. But if i want to trace
>>> power:power_start events, it does not work. After typing
>>>
>>> echo "power:power_start" | sudo tee set_event
>>>
>>> on the console, the trace doesn't contain such events.
>>> power:power_frequency and power:power_end events are reported correctly
>>> by the system. I read in the mailing list that Robert Schoene had a
>>> similiar problem, but with power:power_end events. Is there a known bug
>>> regarding to trace_power_start methods in process.c?
>>>
>> Is this for perf or ftrace? I'm assuming you did this from the debugfs
>> tracing directory. The set_event file is for ftrace not perf.
>>
> It is for perf - i'm interested in event tracing. I used the event
> tracing system like it is described in Documentation/trace/events.txt.
> In addition i wrote a program which uses syscall(__NR_perf_counter_open,
> ... ) to trace power events. But the result is the same -
> power:power_end events are reported, power:power_start events not.
>
> Bye Ronny


Hi, can you please compare the perf and ftrace output to
see if ftrace works while perf doesn't for example?

In perf:
perf record -f -c 1 -a -e power:power_start
^C
perf report

In ftrace:
echo 1 > $DEBUGFS/tracing/events/power/power_start/enable
cat $DEBUGFS/trace_pipe

Thanks.

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