From mboxrd@z Thu Jan  1 00:00:00 1970
From: Namhyung Kim <namhyung@kernel.org>
Subject: Re: usability issues with inlining and backtraces
Date: Wed, 17 Aug 2016 00:13:10 +0900
Message-ID: <20160816151310.GB11382@danjae.aot.lge.com>
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 <87mvkeymyz.fsf@tassilo.jf.intel.com>
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To: Andi Kleen <andi@firstfloor.org>
Cc: Milian Wolff <milian.wolff@kdab.com>, jolsa@redhat.com, linux-perf-users@vger.kernel.org

On Mon, Aug 15, 2016 at 10:13:24AM -0700, Andi Kleen wrote:
> 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.

I think the unwind libs should set entry->ip to al.addr instead of
ip.  The __hists__add_entry() sets hist_entry->ip using al->addr.

Thanks,
Namhyung