RE: [PATCH 01/14] perf/x86: Introduce PERF_RECORD_OVERHEAD

[Liang, Kan]

> On Thu, Nov 24, 2016 at 01:56:51PM +0000, Liang, Kan wrote:
> >
> >
> > >
> > > On Thu, Nov 24, 2016 at 01:45:28PM +0000, Liang, Kan wrote:
> > > > > I think we should make this optional/configurable like the rest
> > > > > of the aux events, like below..
> > > > >
> > > >
> > > > The overhead logging only happens when event is going to be
> > > > disabled or the task is scheduling out. It should not be much and
> expensive.
> > > >
> > > > Peter,
> > > >
> > > > What do you think?
> > > > Should we make it configurable?
> > >
> > > Is there a downside to having it optional?
> >
> > NO. There will be no overhead information dumped into perf.data. Just
> > like current implementation.
> 
> old perf tools will get unexpected events if it's not optional
>

That's expected because a new record type is introduced.
 
OK, I will make it configurable. Anyway, there is nothing to lose. :)

Thanks,
Kan

> [root@ibm-x3650m4-01 perf]# ./perf c2c record -ag ^C[ perf record: Woken
> up 1 times to write data ]
> Warning:
> Found 1 unknown events!
> 
> Is this an older tool processing a perf.data file generated by a more recent
> tool?
> 
> If that is not the case, consider reporting to linux-kernel@xxxxxxxxxxxxxxxx
> 
> [ perf record: Captured and wrote 2.333 MB perf.data (9370 samples) ]
> 
> 
> jirka