linux-kernel - Re: Scrolling down broken with "perf top --hierarchy"

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Date:   Fri, 7 Oct 2016 11:35:45 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Markus Trippelsdorf <markus@...ppelsdorf.de>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Jiri Olsa <jolsa@...nel.org>
Subject: Re: Scrolling down broken with "perf top --hierarchy"

Em Fri, Oct 07, 2016 at 01:53:57PM +0900, Namhyung Kim escreveu:
> Cc-ing perf maintainers,
> 
> On Fri, Oct 07, 2016 at 06:32:29AM +0200, Markus Trippelsdorf wrote:
> > On 2016.10.07 at 13:22 +0900, Namhyung Kim wrote:
> > > On Fri, Oct 07, 2016 at 05:51:18AM +0200, Markus Trippelsdorf wrote:
> > > > On 2016.10.07 at 10:17 +0900, Namhyung Kim wrote:
> > > > > On Thu, Oct 06, 2016 at 06:33:33PM +0200, Markus Trippelsdorf wrote:
> > > > > > Scrolling down is broken when using "perf top --hierarchy".
> > > > > > When it starts up everything is OK and one can scroll up and down to all
> > > > > > entries. But as further and further new entries get added to the list,
> > > > > > scrolling down is blocked (at the position of the last entry that was
> > > > > > shown directly after startup).
> > > > > 
> > > > > I think below patch will fix the problem.  Please check.
> > > > 
> > > > Yes. It works fine now. Many thanks.
> > > 
> > > Good.  Can I add your Tested-by then?
> > 
> > Sure.
> 
> Ok, I'll send a formal patch with it.
> 
> > 
> > (And in the long run you should think of making "perf top --hierarchy"
> > the default for perf top, because it gives a much better (uncluttered)
> > overview of what is going on.)
> 
> I think it's a matter of taste.  Some people prefer to see the top
> single function or something (i.e. current behavior) while others
> prefer to see a higher-level view.
> 
> But we can think again about the default at least for perf-top.  I
> worried about changing default behavior because last time we did it
> for children mode many people complained about it.  But I do think the
> hierarchy mode is useful for many people though.

So, I think in such cases we could experiment with asking the user about
switching to the new mode by showing a popup message telling what it is
about, if the user says "yes, I want to try it" switch to it and if
another hotkey is pressed later, write what was chosen (yes, switch to
this new mode, no, I don't like it, don't pester me about it anymore) to
its ~/.perfconfig file so that next time it goes straight to this new
mode, else don't ask the user again and keep using whatever mode was
there already.

What do you think?

- Arnaldo

> Hmm.. I thought that it already has a config option to enable hierarch
> mode by default, but I cannot find it now.
> 
> Thanks,
> Namhyung