Re: [PATCH 5/9] perf: Adding sysfs group format attribute for pmu device

[Jiri Olsa <jolsa@redhat.com>]

On Wed, Feb 01, 2012 at 03:18:52PM +0100, Peter Zijlstra wrote:
> On Wed, 2012-02-01 at 14:13 +0100, Jiri Olsa wrote:
> > > Are you are suggesting that a single event could use multiple groups
> > > because they may share some common fields, such as the event code?  If
> > > so, I think that might be confusing.   I think it would be better to
> > > have every group fully lay out the bits in the config{,1,2} fields so
> > > that you only need to specify one group per event, even if that leads to
> > > some redundancy (e.g. group1..n all have an eventcode field.)
> > 
> > ok, it'd be the 'cpu::group1/config=1,config1=2,config2=3/u' then..
> > 
> > but let's see what Peter thinks about this, since he first suggested
> > to 'fix' this by having separate pmu drivers.. not format groups :) 
> 
> I'm not convinced we need the whole grouping thing. Even x86 might have
> overlapping definitions, even for a single PMU (config1 contents will
> radically differ depending on the actual events used for instance).

well, I think let's go with what we have now, and see if need/want
to care about format groups later after we use it for a while..

since the "cpu/..../" syntax is new interface, there should be no
problem to change it

> 
> All we should do is warn the user when overlapping masks are used in a
> single event definition and other than that just do as they tell us.

that should be no problem..
do you want it in to take this.. ooor is later ok ;)

jirka

> 
> PMUs can always do an informal namespace thing if really needed, eg. by
> using a consistent prefix.
>