linux-kernel - Re: [PATCH 6/7] perf report: mark inlined frames in output by " (inlined)" suffix

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Date:   Tue, 6 Jun 2017 10:33:49 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Milian Wolff <milian.wolff@...b.com>
Cc:     "linux-kernel@...r.kernel.org" <Linux-kernel@...r.kernel.org>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Yao Jin <yao.jin@...ux.intel.com>, kernel-team@....com
Subject: Re: [PATCH 6/7] perf report: mark inlined frames in output by "
 (inlined)" suffix

On Sat, Jun 3, 2017 at 10:51 PM, Milian Wolff <milian.wolff@...b.com> wrote:
> On Montag, 22. Mai 2017 14:48:18 CEST Namhyung Kim wrote:
>> On Thu, May 18, 2017 at 09:34:10PM +0200, Milian Wolff wrote:
>> > The original patch that introduced inline frame output in the
>> > various browsers used this suffix already. The new centralized
>> > approach that uses fake symbols for inlined frames was missing
>> > this approach so far.
>> >
>> > Instead of changing the symbol name itself, we only print the
>> > suffix where needed. This allows us to efficiently lookup
>> > the symbol for a given name without first having to append the
>> > suffix before the lookup.
>>
>> You also need to do same thing for hist_entry__sym_snprintf().
>
> Hey Namhyung,
>
> I'm working on the next iteration of this patch series, the WIP can be found
> here: https://github.com/milianw/linux/tree/wip/distinguish-inliners.
>
> I just stumbled upon another issue:
>
> ~~~~~
> perf report --inline -s srcline -g srcline  --stdio -g none
>     61.22%     0.00%  main+378
>     61.22%     0.00%  std::_Norm_helper<true>::_S_do_it<double>+378
>     61.22%     0.00%  std::__complex_abs+378
>     61.22%     0.00%  std::abs<double>+378
>     61.22%     0.00%  std::norm<double>+378
> ~~~~~
>
> The problem here is that the srcline in the hist is detached from what we
> actually produce in the callchain nodes. We will have to somehow hand through
> the srcline from the callchain node to the hist entry, but this seems to be a
> super large invasive change - which is why I need your input on how to resolve
> this.
>
> The current API seems to pass the data around mostly using the addr_location
> struct, which is usually constructed on the stack and not always memset to
> zero. As such, my initial plan of adding a srcline member there would require
> me to go through all the code to ensure that we memset the struct to zero...
>
> Alternatively, I'd have to change the API of hist_iter_ops, to let the
> callback take another `const char **srcline` out parameter. This is also going
> to be quite a large invasive change.
>
> Do you have any suggestions on how to make this work?

I think passing srcline via addr_location might not be very invasive
since it calls machine__resolve() in most cases.  Missing places that
set al->sym should set al->srcline as well IMHO.

Thanks,
Namhyung