linux-kernel - Re: [PATCH 2/3] perf tools: Add callchain order support for libunwind DWARF unwinder

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Date:	Wed, 18 Nov 2015 08:54:31 +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>,
	lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Milian Wolff <milian.wolff@...b.com>
Subject: Re: [PATCH 2/3] perf tools: Add callchain order support for
 libunwind DWARF unwinder

On Wed, Nov 18, 2015 at 12:13:08PM +0800, Wangnan (F) wrote:

SNIP

>      3.38%  a.out    a.out             [.] funcc
>               |
>               ---funcc
>                  |
>                  |--2.70%-- funcb
>                  |          funca
>                  |          main
>                  |          __libc_start_main
>                  |          _start
>                  |
>                   --0.68%-- 0
> 
> 
> I'm not sure whether we can regard this behavior changing as a bugfix? I
> think
> there may be some reason the original code explicitly avoid creating an '0'
> entry.
> 
> Then I tried to find why perf can't get call frame on my case, and
> I guess there's something wrong whe dealing with 'call' command, because
> the instruction on it I can't get callchain from libunwind is a 'callq':
> 
>   ...
>   4005bf:       be 00 00 00 00          mov    $0x0,%esi
>   4005c4:       48 89 c7                mov    %rax,%rdi
>   4005c7:       e8 74 fe ff ff          callq  400440 <gettimeofday@plt>
>                 us2 = tv2.tv_sec * 1000000 + tv2.tv_usec;
>   4005cc:       48 8b 04 24             mov    (%rsp),%rax
>   ...
> 
> But this is another problem, we can discuss it in a new thread.

so the problem is you dont see the gettimeofday call at the end?

could you share the test code?

thanks,
jirka
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