interpret the result of perf stat

[Peter Teoh]

This is from LinuxKongress 2010:

The New Linux 'perf' Tools - Vger

http://vger.kernel.org/~acme/perf/lk2010-perf-paper.pdf

http://www.linux-kongress.org/2010/slides/lk2010-perf-acme.pdf

Enjoy....

On Sun, Oct 9, 2011 at 2:42 AM, Zheng Da <zhengda1936 at gmail.com> wrote:
> 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
>>
>



-- 
Regards,
Peter Teoh