Messages in this thread | | | Date | Thu, 2 Mar 2017 10:44:11 +0000 | From | Mark Rutland <> | Subject | Re: ARM64 perf stacktraces on tracepoint events |
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[Adding James, Takahiro-san, and Will, for stacktracing and arm64 perf]
On Wed, Mar 01, 2017 at 04:42:17PM -0800, Joel Fernandes wrote: > Hi, > > On 3.18 kernel running on an arm64 device, I tried running: > perf record -a -g -e sched:sched_wakeup > > I was expecting something like the output at: > www.brendangregg.com/perf.html > > But I don't see stacktraces, could I be missing any patches you could > point me to?
I can't spot much obvious, looking at arm64's stacktrace.c and perf_callchain.c since v3.18. There's commit:
9702970c7bd3e2d6 (Revert "ARM64: unwind: Fix PC calculation")
... though that was Cc'd stable.
I can't immediately see why that would truncate unwinding, though I'm also not sure how perf and ftrace interact here, so I may be missing something obvious.
> I do see stack traces if I do regular perf profiling > (perf record -F 99 -a -g).
> Below is the output I get. Thanks for any insight into this. > > Regards, > Joel > > sailfish:/data # ./perf report > # Samples: 22 of event 'sched:sched_wakeup' > # Event count (approx.): 410333 > # > # Children Self Trace output > # ........ ........ > ............................................................. > # > 61.29% 61.29% comm=ksoftirqd/0 pid=3 prio=120 success=1 target_cpu=000 > | > ---0 > > 33.25% 33.25% comm=hw pid=12777 prio=120 success=1 target_cpu=002 > | > ---0 > > 2.46% 2.46% comm=kworker/u8:2 pid=12482 prio=120 success=1 > target_cpu=002 > | > ---0 > > 1.39% 1.39% comm=migration/2 pid=21 prio=0 success=1 target_cpu=002 > | > ---0
FWIW, on a recent HEAD (86292b33d4b79ee0), I see reasonable looking backtraces, e.g.
77.48% 0.00% swapper [kernel.kallsyms] [k] do_idle | ---do_idle | |--68.84%--call_cpuidle | cpuidle_enter | cpuidle_enter_state | | | --61.05%--el1_irq | gic_handle_irq | __handle_domain_irq | irq_exit | __do_softirq | | | |--22.29%--run_timer_softirq
Thanks, Mark.
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