Re: usability issues with inlining and backtraces

[Andi Kleen <andi@firstfloor.org>]

Milian Wolff <milian.wolff@kdab.com> writes:

> On Monday, August 15, 2016 11:32:33 AM CEST Milian Wolff wrote:
>> On Monday, June 13, 2016 6:07:13 PM CEST Milian Wolff wrote:
>> > Ping?
>> > 
>> > Andi, I'd be very interested in your answers on my questions below. Most
>> > notably, `srcline` with `--call-graph ...,address` seems to be highly
>> > buggy
>> > for me.
>> 
>> Reping again.
>> 
>> Andi, or anyone else - I would really appreciate some more feedback on my
>> questions below.
>> 
>> I esp. wonder how to leverage srcline and addresses in the call-graph, as
>> that has the potential to greatly increase perf's value to me.
>
> OK, I have found at least two culprits that partially explain the behavior.
>
> On one hand, I'm simply missing debug information for some libraries, such as 
> libm, libc etc. pp. Due to that, the addr2line step fails and sym+offset is 
> displayed.
>
> On the other hand, there seems to be a bug in perf: 
>
> When hist_entry__get_srcline calls get_srcline I see from debug output
>
> he->ip=307e, sym=main -> rip_obj2dump=40307e -> mandelbrot.h:39
>
> But in callchain_list__sym_name, I see:
>
> cl->ip=40373d, sym=main -> rip_obj2dump=80373d-> main+8390413
>
> So it seems like the callchain_list is missing a normalization step that is 
> applied to the IP addresses stored in hist_entry. Can someone point me into 
> the right direction?
>
> If I change callchain_list__sym_name to pass cl->ip - cl->ms.map->start to 
> map__rip_2objdump this feature works much better for me, but I doubt that this 
> is the correct fix.

Yes it's something like that. Namhyung or Jiri probably know
what the right fix would be.

-Andi