Re: [PATCH 02/14] perf trace: Apply new perf_mmap__read_event() interface

[Liang, Kan]

On 3/2/2018 6:30 PM, Jiri Olsa wrote:
> On Thu, Mar 01, 2018 at 06:08:59PM -0500, kan.liang@xxxxxxxxxxxxxxx wrote:
> > From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> >
> > The perf trace still use the legacy interface.
> >
> > Apply the new perf_mmap__read_event() interface for perf trace.
> >
> > No functional change.
> >
> > Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> > ---
> >   tools/perf/builtin-trace.c | 11 +++++++++--
> >   1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> > index e7f1b18..a46644f 100644
> > --- a/tools/perf/builtin-trace.c
> > +++ b/tools/perf/builtin-trace.c
> > @@ -2472,8 +2472,14 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
> >   
> >   	for (i = 0; i < evlist->nr_mmaps; i++) {
> >   		union perf_event *event;
> > +		struct perf_mmap *md;
> > +		u64 end, start;
> >   
> > -		while ((event = perf_evlist__mmap_read(evlist, i)) != NULL) {
> > +		md = &evlist->mmap[i];
> > +		if (perf_mmap__read_init(md, 0, &start, &end) < 0)
> > +			continue;
>
> should we break the loop if this returns -EINVAL?

It only means the ring buffer is broken for current mmaps.
For others, the data should still be good.
I don't think we should drop them by breaking the loop.

Also, the -EINVAL is only valid for overwrite mode. It is impossible to 
return -EINVAL in current code.

Thanks,
Kan

> jirka
>
> > +
> > +		while ((event = perf_mmap__read_event(md, 0, &start, end)) != NULL) {
> >   			struct perf_sample sample;
> >   
> >   			++trace->nr_events;
> > @@ -2486,7 +2492,7 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
> >   
> >   			trace__handle_event(trace, event, &sample);
> >   next_event:
> > -			perf_evlist__mmap_consume(evlist, i);
> > +			perf_mmap__consume(md, 0);
> >   
> >   			if (interrupted)
> >   				goto out_disable;
> > @@ -2496,6 +2502,7 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
> >   				draining = true;
> >   			}
> >   		}
> > +		perf_mmap__read_done(md);
> >   	}
> >   
> >   	if (trace->nr_events == before) {
> > --
> > 2.4.11