[RFC] Re: [PATCHSET 0/8] perf tools: Support multiple keys in a single hierarchy level (v1)

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Thu, Mar 03, 2016 at 08:16:36AM +0900, Namhyung Kim escreveu:
> On Wed, Mar 02, 2016 at 01:25:07PM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Mar 03, 2016 at 01:12:00AM +0900, Namhyung Kim escreveu:
> > > This implements what Arnaldo suggested in previous discussion of
> > > hierarchy patchset [1].  Originally each level in a hierarchy can have
> > > a single sort key in it, but with patches it's possible to have more
> > > than one sort keys.  I added the struct perf_hpp_list_node and carry
> > > it to group output formats (hpp_fmt) in a single level.

> > > I used ':' character instead of '+' as suggested since the '+' was
> > > also used to extend existing sort keys (like -s '+cpu').

> > Could we use ';' instead? That is associated with lists as well, i.e.:

> >   perf report --hierarchy -s prev_pid;prev_comm,next_pid;next_comm

> > What do you think? Others?
 
> The ';' is interpreted by shell first, so it needs to be quoted.
 
>   $ perf report -s comm,dso;sym
>   bash: sym: command not found

Right, but this is not some really common operation, so asking for it to
be quoted is not such an unreasonable demand, and I continue thinking
that ':' should be left for other purposes, ',' and ';' are better
suited for expressing lists.

We will/have stumble/d in this more times, like when we added { for groups:

  # perf record -e cycles,instructions usleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.017 MB perf.data (4 samples) ]
  # perf report --header-only | grep group
  # 
  # perf record -e {cycles,instructions} usleep 1
  Workload failed: No such file or directory
  # perf record -e '{cycles,instructions}' usleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.017 MB perf.data (4 samples) ]
  # perf report --header-only | grep group
  # group: {cycles,instructions}
  # 

We should try to use tokens that already have some strong meaning
associated to them instead of using those that are more easily
available, otherwise our mumbo jumbo will grow even more unwieldly 8-/

In fact I think that in this case we could even make it look more like
natural languages and use:

  perf report --hierarchy -s 'prev_pid,prev_comm;next_pid,next_comm'

To ask for:
 
      prev_pid  prev_comm
            next_pid  next_comm          
      - 1234      bash
              5678     firefox
      + 8912      hexchat

I.e. if ';' is present, it is the separator for each hierarchy level,
with ',' being used for stating the per-hierarchy level fields.

Ingo, what do you think?

- Arnaldo