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

[Jiri Olsa]

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

[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