On Tue, Oct 4, 2011 at 9:53 AM, Peter Teoh <htmldeveloper@xxxxxxxxx> wrote:
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:
On Sun, Oct 2, 2011 at 5:07 AM, Zheng Da <zhengda1936@xxxxxxxxx> wrote:
> Hello,
>
> I start to use perf to profile my program, but I'm not quite sure if I
> understand some events.
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:
�
> 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.
�
-->
> Thanks,
> Da
>
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Regards,
Peter Teoh
Regards,
Peter Teoh
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