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... Thanks, Da On Sat, Oct 8, 2011 at 11:18 AM, Peter Teoh <htmldeveloper@gmail.com> wrote:
On Thu, Oct 6, 2011 at 10:39 PM, Zheng Da <zhengda1936@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@gmail.com> wrote:
On Tue, Oct 4, 2011 at 9:53 AM, Peter Teoh <htmldeveloper@gmail.com> wrote:
On Sun, Oct 2, 2011 at 5:07 AM, Zheng Da <zhengda1936@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/Concept... 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