On Tue, Oct 4, 2011 at 9:53 AM, Peter Teoh <[email protected]> wrote:
> > On Sun, Oct 2, 2011 at 5:07 AM, Zheng Da <[email protected]> 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. > > > > Thanks, > > Da > > > > _______________________________________________ > > Kernelnewbies mailing list > > [email protected] > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > > > > -- > Regards, > Peter Teoh > > -- Regards, Peter Teoh
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