linux-kernel - Re: [PATCH 13/16] perf callchain: Switch default to 'graph,0.5,caller'

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Date:	Tue, 20 Oct 2015 10:06:51 -0300
From:	Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:	Chandler Carruth <chandlerc@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Brendan Gregg <brendan.d.gregg@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Borislav Petkov <bp@...e.de>, David Ahern <dsahern@...il.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Wang Nan <wangnan0@...wei.com>
Subject: Re: [PATCH 13/16] perf callchain: Switch default to
 'graph,0.5,caller'

Em Tue, Oct 20, 2015 at 02:19:50PM +0200, Frederic Weisbecker escreveu:
> On Tue, Oct 20, 2015 at 09:00:34AM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Mon, Oct 19, 2015 at 05:16:53PM -0700, Brendan Gregg escreveu:
> > So are you advocating different defaults, one for --stdio (callee),
> > another for --tui, --gtk (caller)?

> > This is all configurable via ~/.perfconfig :-\

> > Indeed, finding a default that is deemed adequate for most people is,
> > ho-hum, difficult 8-)

> Most uses I've seen on LKML by the past involved callee because people
> mostly look at the precise point where a performance issue is.

A good chunk of that was because that was the default? 

> IMHO changing that order is not a good idea. Unless many users complained
> about it.

Perhaps there are not that many users of callchains because the default
is not what they're used to see?

Motivation for the change came from a video from Chandler, that
resurfaced the callchain default issue, Chandler?

Anedoctally, he tweeted about it and people seemed to like it.

> > Ingo, what do you think?

What about providing a hotkey, in the tui, to toggle caller/callee
views, and another hotkey to save that in ~/.perfconfig so that becomes
the new default?

In the --stdio mode we need to add a warning in the first lines,
something like:

# This is caller (or callee) based, please use --callchain ... to change it

One way or the other people will disagree, so making it easy to switch
to the preferred way would be nice to have?

- Arnaldo
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