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

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Date:   Mon, 5 Mar 2018 23:37:54 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Du, Changbin" <changbin.du@...el.com>
Cc:     Namhyung Kim <namhyung@...nel.org>, 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

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?

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

> 
> 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 

thanks,
jirka