linux-kernel - Re: [RESEND PATCH] perf sched map: re-annotate shortname if thread comm changed

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Date:   Tue, 6 Mar 2018 08:16:00 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     "Du, Changbin" <changbin.du@...el.com>, acme@...nel.org,
        peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        kernel-team@....com
Subject: Re: [RESEND PATCH] perf sched map: re-annotate shortname if thread
 comm changed

Hi,

On Mon, Mar 05, 2018 at 11:37:54PM +0100, Jiri Olsa wrote:
> On Mon, Mar 05, 2018 at 03:11:36PM +0800, Du, Changbin wrote:
> 
> SNIP
> 
> > > > on the other hand it's simple enough and looks
> > > > like generic solution would be more tricky
> > > 
> > > What about adding perf_sched__process_comm() to set it in the
> > > thread::priv?
> > >
> > I can be done, then thread->comm_changed moves to thread_runtime->comm_changed.
> > Draft code as below. It is also a little tricky.
> > 
> > +int perf_sched__process_comm(struct perf_tool *tool __maybe_unused,
> > +                            union perf_event *event,
> > +                            struct perf_sample *sample,
> > +                            struct machine *machine)
> > +{
> > +       struct thread *thread;
> > +       struct thread_runtime *r;
> > +
> > +       perf_event__process_comm(tool, event, sample, machine);
> > +
> > +       thread = machine__findnew_thread(machine, pid, tid);
> 
> should you use machine__find_thread in here?

Yep, perf_event__process_comm() already created a new thread if needed.
And the return value of it should be checked.


> 
> > +       if (thread) {
> > +               r = thread__priv(thread);
> > +               if (r)
> > +                       r->comm_changed = true;
> > +               thread__put(thread);
> > +       }

Missing return.

> > +}
> > +
> >  static int perf_sched__read_events(struct perf_sched *sched)
> >  {
> >         const struct perf_evsel_str_handler handlers[] = {
> > @@ -3291,7 +3311,7 @@ int cmd_sched(int argc, const char **argv)
> >         struct perf_sched sched = {
> >                 .tool = {
> >                         .sample          = perf_sched__process_tracepoint_sample,
> > -                       .comm            = perf_event__process_comm,
> > +                       .comm            = perf_sched__process_comm,
> > 
> > 
> > But I'd keep 'comm_changed' where 'shortname' is defined. I think they should appears
> > togother. And 'shortname' is only used by sched command, too.
> 
> they can both go to struct thread_runtime then

Agreed.


> 
> > 
> > So I still prefer my privous simpler change. Thanks!
> 
> I was wrong thinking that the amount of code
> making it sched specific would be biger
> 
> we're trying to keep the core structs generic,
> so this one fits better 

Right.

Thanks,
Namhyung