Re: [PATCH/RFC v3] perf core: Allow setting up max frame stack depth via sysctl

[Arnaldo Carvalho de Melo]

Em Tue, Apr 26, 2016 at 01:02:34PM -0700, Brendan Gregg escreveu:
> On Mon, Apr 25, 2016 at 5:49 PM, Brendan Gregg <brendan.d.gregg@xxxxxxxxx> wrote:
> > On Mon, Apr 25, 2016 at 5:47 PM, Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx> wrote:
> >> Em Mon, Apr 25, 2016 at 05:44:00PM -0700, Alexei Starovoitov escreveu:
> >>> yep :)
> >>> hopefully Brendan can give it another spin.
> >>
> >> Agreed, and I'm calling it a day anyway, Brendan, please consider
> >> retesting, thanks,
> >
> > Will do, thanks!
> 
> Looks good.
> 
> I started with max depth = 512, and even that was still truncated, and
> had to profile again at 1024 to capture the full stacks. Seems to
> generally match the flame graph I generated with V1, which made me
> want to check that I'm running the new patch, and am:
> 
> # grep six_hundred_forty_kb /proc/kallsyms
> ffffffff81c431e0 d six_hundred_forty_kb
> 
> I was mucking around and was able to get "corrupted callchain.
> skipping..." errors, but these look to be expected -- that was

Yeah, thanks for testing!

And since you talked about userspace without frame pointers, have you
played with '--call-graph lbr'?

- Arnaldo

> profiling a binary (bash) that doesn't have frame pointers. Some perf
> script -D output:
> 
> 16 3204735442777 0x18f0d8 [0x2030]: PERF_RECORD_SAMPLE(IP, 0x1):
> 18134/18134: 0xffffffff8118b6a4 period: 1001001 addr: 0
> ... FP chain: nr:1023
> .....  0: ffffffffffffff80
> .....  1: ffffffff8118b6a4
> .....  2: ffffffff8118bc47
> .....  3: ffffffff811d8c85
> .....  4: ffffffff811b18f8
> .....  5: ffffffff811b2a55
> .....  6: ffffffff811b5ea0
> .....  7: ffffffff810663c0
> .....  8: ffffffff810666e0
> .....  9: ffffffff817b9d28
> ..... 10: fffffffffffffe00
> ..... 11: 00000000004b45e2
> ..... 12: 000000000000610f
> ..... 13: 0000000000006110
> ..... 14: 0000000000006111
> ..... 15: 0000000000006112
> ..... 16: 0000000000006113
> ..... 17: 0000000000006114
> ..... 18: 0000000000006115
> ..... 19: 0000000000006116
> ..... 20: 0000000000006117
> [...]
> ..... 1021: 000000000000650b
> ..... 1022: 000000000000650c
>  ... thread: bash:18134
>  ...... dso: /lib/modules/4.6.0-rc5-virtual/build/vmlinux
> bash 18134 [016]  3204.735442:    1001001 cpu-clock:
> 
> Brendan