Re: [PATCH] perf/tools : remove default system_wide in sched record

[chengjian (D)]

On 2017/10/25 10:23, Namhyung Kim wrote:
> On Tue, Oct 24, 2017 at 10:46:44AM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Tue, Oct 24, 2017 at 03:45:34PM +0800, Cheng Jian escreveu:
> > > When running perf sched record, there is a bug.
> > >
> > > It's system_wide when we specify a command line.
> > Humm, isn't this because if you trace just a workload you will miss the
> > sched-in events?
> >
> > Perhaps with PERF_RECORD_SWITCH we can solve that... I.e. still get the
> > sched-in events while tracing just one workload, not requiring
> > system_wide like it is the case now, right?
> Yes, but it will lose other task's comm, also (at least) sched-wakeup
> (from other task) events are still needed.
>
> Thanks,
> Namhyung

I found that if the parameters -p and -a were specified at the same time,
PID/TID(-p/-t) would overwrite SYSTEM_WIDE (-a) in target__validate( ).

If we don't specify a process(-p) or a workload, it will make system 
wide (-a)
as the default target.

    /* Make system wide (-a) the default target. */
    if (!argc && target__none(&rec->opts.target))
        rec->opts.target.system_wide = true;

So don't -a and -p should have the same operation and feedback?

It also lose some events when use -p.