interpret the result of perf stat

[Peter Teoh]

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
> 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?
>
> Thanks,
> Da
>
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-- 
Regards,
Peter Teoh
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