linux-kernel - Re: [BUG REPORT] perf tools: x86_64: Broken calllchain when sampling taken at 'callq' instruction

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Date:	Wed, 18 Nov 2015 09:48:42 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	"Wangnan (F)" <wangnan0@...wei.com>
Cc:	Jiri Olsa <jolsa@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	David Ahern <dsahern@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Milian Wolff <milian.wolff@...b.com>,
	linux-kernel@...r.kernel.org, pi3orama <pi3orama@....com>,
	lizefan 00213767 <lizefan@...wei.com>
Subject: Re: [BUG REPORT] perf tools: x86_64: Broken calllchain when sampling
 taken at 'callq' instruction

On Wed, Nov 18, 2015 at 03:20:36PM +0800, Wangnan (F) wrote:

SNIP

> 
> Then use perf to trace it:
> 
> # ./pref record  -g -F 9 --call-graph dwarf ./test_dwarf_unwind
> # ./perf report  --no-children --stdio
>      ...
>      1.23%  test_dwarf_unwi  test_dwarf_unwind  [.] funcc
>             |
>             ---funcc
>                |
>                |--0.62%-- funcb
>                |          funca
>                |          main
>                |          __libc_start_main
>                |          _start
>                |
>                 --0.62%-- 0   <-- I applied Jiri's patch in [1] so see this
> 0,
>                                   which indicates a broken call chain.

can't see this case after multiple running your test,
just the 'end-of-the-callchain' zeros

    49.14%  test_dwarf_unwi  [vdso]             [.] __vdso_gettimeofday  
            |
            ---__vdso_gettimeofday
               funcc
               funcb
               funca
               main
               __libc_start_main
               _start
               0

    40.78%  test_dwarf_unwi  [vdso]             [.] 0x0000000000000987   
            |
            ---0x7ffe28ab7987
               __vdso_gettimeofday
               funcc
               funcb
               funca
               main
               __libc_start_main
               _start
               0


what kernel do you have?

jirka
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