Re: Perf event for Wall-time based sampling?

[Namhyung Kim <namhyung@kernel.org>]

2014-09-19 (금), 16:53 +0200, Milian Wolff:
> On Friday 19 September 2014 11:33:40 Arnaldo Carvalho de Melo wrote:
> > Em Fri, Sep 19, 2014 at 02:59:55PM +0900, Namhyung Kim escreveu:
> > > Hi Arnaldo and Millan,
> > > 
> > > On Thu, 18 Sep 2014 16:17:13 -0300, Arnaldo Carvalho de Melo wrote:
> > > > Em Thu, Sep 18, 2014 at 06:37:47PM +0200, Milian Wolff escreveu:
> > > >> That would indeed be very welcome. There are multiple "defaults" in
> > > >> perf which I find highly confusing. The --no-children above e.g.
> > > >> could/should probably be the default, no? Similar, I find it extremely
> > > >> irritating that `perf report -g`> > 
> > > > It was, this is something we've actually been discussing recently: the
> > > > change that made --children be the default mode. That is why I added
> > > > Namhyung and Ingo to the CC list, so that they become aware of more
> > > > reaction to this change.
> > > 
> > > Yeah, we should rethink about changing the default now.  Actually I'm
> > > okay with the change, Ingo what do you think?
> > > 
> > > >> defaults to `-g fractal` and not `-g graph`.
> > > >> 
> > > >> 100% foo
> > > >> 
> > > >>   70% bar
> > > >>   
> > > >>     70% asdf
> > > >>     30% lalala
> > > >>   
> > > >>   30% baz
> > > >> 
> > > >> is much harder to interpret than
> > > >> 
> > > >> 100% foo
> > > >> 
> > > >>   70% bar
> > > >>   
> > > >>     49% asdf
> > > >>     21% lalala
> > > >>   
> > > >>   30% baz
> > > 
> > > I also agree with you. :)
> > > 
> > > > But the question then is if this is configurable, if not that would be a
> > > > first step, i.e. making this possible via some ~/.perfconfig change.
> > > 
> > > Yes, we have record.call-graph and top.call-graph config options now so
> > > adding a new report.call-graph option should not be difficult.  However
> > > I think it'd be better being call-graph.XXX as it can be applied to all
> > 
> > No problem, with sourcing being supported in ~/.perfconfig, we can have
> > as many #include call-graph.XXX as needed, multiple levels of includes
> > and all.
> > 
> > > other subcommands transparently.
> > > 
> > > What about like below?
> > > 
> > > [call-graph]
> > > 
> > >   mode = dwarf
> > >   dump-size = 8192
> > >   print-type = fractal
> > >   order = callee
> > >   threshold = 0.5
> > >   print-limit = 128
> > >   sort-key = function
> > 
> > Milian, does this provide what you expect? How would we call this
> > specific call-graph profile?
> 
> print-type should be graph, not fractal. Otherwise it sounds good to me. But 
> how would one use it? I tried putting it into ~/.perfconfig, but apparently my 
> 3.16.2-1-ARCH Perf does not support this feature yet? How/when would that 
> config be used? As soon as one does "perf record -g" (for mode and dump-size) 
> or "perf report" (for a perf.data with call graphs)? That would be very 
> useful!

This is a proposal for new config items which can be included into the
~/.perfconfig file.  You can change it as you want later and it should
apply to default behavior of perf record -g and perf report.

Thanks,
Namhyung