linux-kernel - Re: [PATCH] perf tools: update docs regarding kernel/user space unwinding

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Message-ID: <C8021C4E-2764-47CE-AF79-10823C7FDBB2@gmail.com>
Date:   Fri, 27 Mar 2020 17:17:59 -0300
From:   Arnaldo Melo <arnaldo.melo@...il.com>
To:     Tony Jones <tonyj@...e.de>
CC:     linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf tools: update docs regarding kernel/user space unwinding



On March 27, 2020 5:09:34 PM GMT-03:00, Tony Jones <tonyj@...e.de> wrote:
>On Thu, Mar 26, 2020 at 04:32:26PM -0500, Paul Clarke wrote:
>> > +		and 'lbr'.  The value 'dwarf' is effective only if libunwind
>> > +		(or a recent version of libdw) is present on the system;
>> > +		the value 'lbr' only works for certain cpus. The method for
>> > +		kernel space is controlled not by this option but by the
>> > +		kernel config (CONFIG_UNWINDER_*).
>> 
>> Your changes are just copying the old text, so this isn't a criticism
>of your patches.
>> 
>> Do we have information to replace "a recent version of libdw", which
>will quickly get stale?
>
>Hi Paul.
>
>The original "(libunwind or a recent version of libdw)" text was from
>Feb 2016.   So a while ago.

Unfortunate wording, would be better to have the version where the required feature was added to libdw.

>
>bd0419e2a5a9f requires >= 0.157 but this is for probing.  0a4f2b6a3ba50
>specifies >= 0.158 but I see no mention of 
>why in the commit but since it's from 2014 and elfutils is now at
>0.178,  I think it's safe to just remove the 
>reference.
>
>As an aside, there is a lot of detail in perf-config.txt that's
>available in some of the other subcomands help files.
>Seems a good way for things to get stale.   It could also do with some
>grammatical cleanup.

English as a second language, many contributors, please consider sending fixes, would be really appreciated,

Thanks,

- Arnaldo
>
>Tony

-- 
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