interpret the result of perf stat

[Zheng Da]

Hey Peter,

If you are talking about the documentation of performance counters, we
can find very complete reference
http://software.intel.com/sites/products/documentation/hpc/amplifierxe/en-us/lin/ug_docs/reference/index.htm

Thanks,
Da

On Sat, Oct 8, 2011 at 11:18 AM, Peter Teoh <htmldeveloper at gmail.com> wrote:
>
>
> On Thu, Oct 6, 2011 at 10:39 PM, Zheng Da <zhengda1936 at gmail.com> wrote:
>>
>> Thank you, Peter. I didn't realize Intel has explained all performance
>> counters in its manual, and I was desperately looking for more
>> detailed explanation on the Internet.
>>
>> On Mon, Oct 3, 2011 at 11:19 PM, Peter Teoh <htmldeveloper at gmail.com>
>> wrote:
>> >
>> >
>> > On Tue, Oct 4, 2011 at 9:53 AM, Peter Teoh <htmldeveloper at gmail.com>
>> > wrote:
>> >>
>> >> On Sun, Oct 2, 2011 at 5:07 AM, Zheng Da <zhengda1936 at gmail.com> wrote:
>> >> > Hello,
>> >> >
>> >> > I start to use perf to profile my program, but I'm not quite sure if
>> >> > I
>> >> > understand some events.
>> >>
>> >> Firstly perf is using hardware to read these performance information.
>> >> So
>> >> for intel CPU, depending on the different model, u can find the
>> >> relevant
>> >> information in the reference manual from Intel here:
>> >>
>> >> http://www.intel.com/Assets/en_US/PDF/manual/248966.pdf
>> >>
>> >> In particular, the various model of Intel CPU is listed in page xvii,
>> >> and
>> >> along with it are the various performance information u can extract out
>> >> -
>> >> the last item is the BUS information (B.6.10).
>> >>
>> >> > First, perf can profile bus cycles. Is it the bus cycles of FSB?
>> >> > Second, what is task clock? It seems to me that task clock is the
>> >
>> > task clock, from reading the implementation in kernel/events/core.c, i
>> > suspect is a software event, not hardware.   Ie, it counts upon each
>> > task
>> > switch.   To quote from core.c:
>> > /*
>> >  * Software event: task time clock
>> >  */
>> > static void task_clock_event_update(struct perf_event *event, u64 now)
>> > {
>> >
>> > More details here:
>> > http://lwn.net/Articles/312720/
>> >
>> >>
>> >> > ticks used by a process. It should include the ticks used in the
>> >> > kernel mode and the user space mode, as long as it is used in the
>> >> > context of the process. I suppose it doesn't count the cycles used by
>> >> > the interrupts such as page faults and softirq, even though the irqs
>> >> > are caused by the process. Is it correct?
>> >
>> > on the contrary, i think it should include, as to exclude these cycles
>> > does
>> > entail stopping the hrtimer.....read into core.c further.
>> I'm disappointed that the information isn't documented somewhere. The
>> developers shouldn't expect users to read the code to understand how
>> to use the tool :(
>>
>
> i suspect it is documented in many places, at here is one good one:
> http://developer.apple.com/library/IOS/#documentation/DeveloperTools/Conceptual/SharkUserGuide/MiscellaneousTopics/MiscellaneousTopics.html#//apple_ref/doc/uid/TP40005233-CH14-SW3
> and from the side, looking at Appendix A, u can see a table of all the
> PerfCounters for ARM11, and then another section will list out for Intel,
> and then PPC etc.....
>
>>
>> BTW, is there any wiki where people can share what they found in the
>> kernel?
>>
>> Thanks,
>> Da
>
>
>
> --
> Regards,
> Peter Teoh
>