Re: [PATCH][RFC 2/23]: SCST core

Ingo Molnar
2008-12-27T11:22:07Z

* Vladislav Bolkhovitin <vst@vlnb.net> wrote:

>> The word graph is actually here to explain here that we not only trace
>> each function call but we can actually retrieve all of the call path of
>> a function and then draw it as if it was C code:
>>
>> 0) ! 108.528 us | }
>> 0) | irq_exit() {
>> 0) | do_softirq() {
>> 0) | __do_softirq() {
>> 0) 0.895 us | __local_bh_disable();
>> 0) | run_timer_softirq() {
>> 0) 0.827 us | hrtimer_run_pending();
>> 0) 1.226 us | _spin_lock_irq();
>> 0) | _spin_unlock_irq() {
>> 0) 6.550 us | }
>> 0) 0.924 us | _local_bh_enable();
>> 0) + 12.129 us | }
>> 0) + 13.911 us | }
>> 0) 0.707 us | idle_cpu();
>> 0) + 17.009 us | }
>> 0) ! 137.419 us | }
>> 0) <========== |
>> 0) 1.045 us | }
>> 0) ! 148.908 us | }
>> 0) ! 151.022 us | }
>> 0) ! 153.022 us | }
>> 0) 0.963 us | journal_mark_dirty();
>> 0) 0.925 us | __brelse();
>
> Unfortunately, it lacks very useful "TASK-PID, CPU#, TIMESTAMP" header
> fields..

those obscure readability in the typical usecases, but you can get them
anytime via using this existing trace_options runtime switch:

echo funcgraph-proc > /debug/tracing/trace_options

resulting in traces like this:

# CPU TASK/PID OVERHEAD/DURATION FUNCTION CALLS
# | | | | | | | |
------------------------------------------
0) distccd-28400 => cc1-30212
------------------------------------------

0) cc1-30212 | 0.270 us | }
0) cc1-30212 | | __do_fault() {
0) cc1-30212 | | filemap_fault() {
0) cc1-30212 | | find_lock_page() {
0) cc1-30212 | 0.453 us | find_get_page();
0) cc1-30212 | 0.997 us | }
0) cc1-30212 | | PageUptodate() {
0) cc1-30212 | 0.266 us | constant_test_bit();
0) cc1-30212 | 0.799 us | }
0) cc1-30212 | 0.379 us | mark_page_accessed();
0) cc1-30212 | 3.275 us | }
0) cc1-30212 | 0.276 us | _spin_lock();
0) cc1-30212 | 0.389 us | page_add_file_rmap();
0) cc1-30212 | | unlock_page() {
0) cc1-30212 | 0.266 us | page_waitqueue();
0) cc1-30212 | 0.381 us | __wake_up_bit();
0) cc1-30212 | 1.442 us | }
0) cc1-30212 | 6.897 us | }
0) cc1-30212 |+ 11.663 us | }
0) cc1-30212 | | up_read() {
0) cc1-30212 | 0.280 us | _spin_lock_irqsave();

Thanks,

Ingo