Messages in this thread | | | Date | Wed, 1 Jul 2009 09:31:39 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH][RFC] Adding information of counts processes acquired how many spinlocks to schedstat |
| |
* Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> wrote:
> Hi, > > I wrote a test patch which add information of counts processes > acquired how many spinlocks to schedstat. After applied this > patch, /proc/<PID>/sched will change like this, > > init (1, #threads: 1) > --------------------------------------------------------- > se.exec_start : 482130.851458 > se.vruntime : 26883.107980 > se.sum_exec_runtime : 2316.651816 > se.avg_overlap : 0.480053 > se.avg_wakeup : 14.999993 > .... > se.nr_wakeups_passive : 1 > se.nr_wakeups_idle : 0 > se.nr_acquired_spinlock : 74483 > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Looks potentially useful - but it would be nice and go one step further and add lock acquire stats as a software-counter.
Perfcounters is a feature of the latest upstream kernel, there's a (still very small) Wiki page about it at:
http://perf.wiki.kernel.org
With perfcounters we can instrument various software properties of the kernel as well, for example the number of page-faults in the system per second:
$ perf stat -a -e page-faults sleep 1
Performance counter stats for 'sleep 1':
294387 page-faults
1.022318527 seconds time elapsed
Now, it would be nice to have a lock-acquire software-counter as well, which would output things like:
$ perf stat -a -e lock-acquires sleep 1
Performance counter stats for 'sleep 1':
294387 lock-acquires
1.022318527 seconds time elapsed
Furthermore, beyond plain counts, doing this would also allow the profiling of lock acquire places: perf record -e lock-acquires and perf report would work fine.
It is really easy to add a new sw counter, check how it is done for the pagefault counter(s), see the uses of PERF_COUNT_SW_PAGE_FAULTS in the following files:
$ git grep -l PERF_COUNT_SW_PAGE_FAULTS
arch/powerpc/mm/fault.c arch/x86/mm/fault.c include/linux/perf_counter.h kernel/perf_counter.c tools/perf/builtin-stat.c tools/perf/design.txt
Would you be interested in having a look at this?
Ingo
| |