linux-kernel - Re: [PATCH 2/2] perf script: flush output stream after events in verbose mode

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Date:   Mon, 22 Oct 2018 15:54:30 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Milian Wolff <milian.wolff@...b.com>
Cc:     acme@...nel.org, jolsa@...nel.org, Linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 2/2] perf script: flush output stream after events in
 verbose mode

On Mon, Oct 22, 2018 at 12:38:57PM +0200, Milian Wolff wrote:

SNIP

> > > > > diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> > > > > index bd468b90801b..ca09b7d2adb7 100644
> > > > > --- a/tools/perf/builtin-script.c
> > > > > +++ b/tools/perf/builtin-script.c
> > > > > @@ -1737,6 +1737,9 @@ static void process_event(struct perf_script
> > > > > *script,
> > > > > 
> > > > >  	if (PRINT_FIELD(METRIC))
> > > > >  	
> > > > >  		perf_sample__fprint_metric(script, thread, evsel, 
> sample, fp);
> > > > > 
> > > > > +
> > > > > +	if (verbose)
> > > > > +		fflush(fp);
> > > > 
> > > > should we call fflush(NULL) to dump all the streams?
> > > > 
> > > > the verbose goes to stderr and fp seems to be stdout byt default
> > > 
> > > stderr isn't buffered, so we don't need to flush it. So personally, I
> > > don't
> > > see a need to dump all streams - fp should be enough? Can you maybe
> > > explain
> > > where it would be required to flush more buffers?
> > 
> > hum, did not know stderr wasn't buffer
> >
> > I think there's perf script feature to store the events data to
> > separate files per each event.. but I guess we don't need to
> > flush them.. we just need to have stdout and stderr in sync IIUC
> 
> Exactly, and that's achieved with this patch form what I see :) Or should we 
> maybe instead call 
> 
> setbuf(fp, NULL);
> 
> in verbose mode?

I think your solution is ok

Acked-by: Jiri Olsa <jolsa@...hat.com>

thanks,
jirka