Re: [PATCH 0/4] perf_event: introduce 'perf timer' to analyze timer's behavior

Xiao Guangrong
2009-12-16T07:42:45Z

Ingo Molnar wrote:

>>>
>> Yeah, it has different unit and looks ugly :-(
>>
>> but, the problem is we can't get HZ in userspace now, i'll export HZ by proc
>> or other way and rectify 'perf timer' output in my next work
>
> We could export HZ as part of the ftrace event format file, in
> /debug/tracing/events/timers/ or so. Not sure what the best way would be to do
> it (without causing runtime overhead in event processing), but we should
> reduce our reliance on /proc and export such instrumentation information via a
> single, coherent interface.
>

Hi ingo,

Um, if we export this value in tracepoint format, it should add for every timer's
tracepoint.

> There's a couple of other 'system settings' values that would be useful to
> expose in such a way - for example the number of online CPUs. (in fact that
> could be exposed as a set of online/offline events plus a way to read the
> current count as well)
>

How about export those values in debugfs/tracing/*? perf tracepoint self depend on
this filesystem.

Thanks,
Xiao