linux-kernel - Re: [PATCH -tip v2 2/6] perf script: add magic word to indicate the failure of resolving symbols

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Message-ID: <4E283A33.1010100@gmail.com>
Date:	Thu, 21 Jul 2011 08:39:47 -0600
From:	David Ahern <dsahern@...il.com>
To:	Akihiro Nagai <akihiro.nagai.hw@...achi.com>
CC:	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	yrl.pp-manager.tt@...achi.com, Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH -tip v2 2/6] perf script: add magic word to indicate the
 failure of resolving symbols

On 07/21/2011 03:36 AM, Akihiro Nagai wrote
>> Evidently I had the shift key down -- s/{}/[]/.  :-) And I see now, for
>> dsoname you have [unknown] and for symname (unknown). Use the same for
>> both. Since () is already used for separating dsoname, use [unknown] for
>> both
> At print_sample_start() in builtin-script.c, there is the code that
> print "(unknown)"
> when perf cannnot resolve the event name.
> 
>     printf("%s: ", evname ? evname : "(unknown)");
> 
> On the other hand, at hist_entry__dso_snprintf() in util/sort.c, there
> is the code
> prints "[unknown]" for unresolvable DSO name.
> 
>     return repsep_snprintf(bf, size, "%-*s", width, "[unknown]");
> 
> In addition, perf uses "[]" for DSO name for example "[kernel.kallsyms]".
> So, I chose it. However, this specification is not easy for user-scripts.
> Should I unify this expression?

That was my thought -- to use the same for both dso and sym if it is
unknown. And since DSO names are wrapped in () use "[unknown]" for both
-- ie., right now the format is  "symname (dsoname)" (though kernel syms
from kallsyms come out as "symname ([kernel.kallsyms])"). With an
unknown it will be "[unknown] (dsoname)" or "[unknown] ([unknown])"
which retains the number of fields in a uniquely parse-able way.

David
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