Re: [PATCH v2 1/3] perf: add PERF_RECORD_NAMESPACES to include namespaces related info

[Hari Bathini]

On Friday 09 December 2016 12:10 AM, Hari Bathini wrote:
> Hi Peter,
>
>
> Sorry for taking so long to respond...
>
>
> On Thursday 24 November 2016 08:40 PM, Peter Zijlstra wrote:
> > On Thu, Nov 24, 2016 at 08:14:29PM +0530, Hari Bathini wrote:
> > > @@ -862,6 +875,19 @@ enum perf_event_type {
> > >        */
> > >       PERF_RECORD_SWITCH_CPU_WIDE        = 15,
> > >   +    /*
> > > +     * struct {
> > > +     *    struct perf_event_header    header;
> > > +     *
> > > +     *    u32                pid, tid;
> > > +     *    u64                time;
> > pid,tid and time are already present in sample_id. Many of the 'legacy'
> > record have redundant information since we added sample_id, but most of
> > the new ones haven't and rely on sample_all being set.
>
> I tried using pid/tid from sample data, but realized that pid/tid in 
> event_id
> could be different from the one in sample data, at least for 
> fork/namespaces
> events, since __perf_event_header__init_id( ) that updates the sample 
> data
> is getting the pid/tid of current task.
>
> I am not sure if it is advisable to change 
> __perf_event_header__init_id( ) for this..?

Hi Peter,

Adding task parameter to __perf_event_header__init_id( ) and doing 
something like..

        perf_event_pid(event, task ? task : current)
        perf_event_tid(event, task ? task : current)


Also, for synthesized events, sample_id is not updated currently. 
Working on it as that
is needed if we want to relay on pid, tid values from sample_id. Let me 
know, if this is
what you had in mind or something else altogether..

Thanks
Hari