[RFC PATCH] perf report: Don't add filtered events to histogram

[Steve Capper]

If one filters events by a single comm in perf report via:
 perf report --no-children -c program-name

perf will elide the comm column as only one comm is filtered in. This
lack of distinction by comm can lead to events being merged in
add_hist_entry that have different comm's, including events that have
been filtered out and filtered in. Ultimately, this can lead to events
disappearing from the report.

If one instead invokes perf via:
 perf report --no-children -c program-name,random-made-up-name

Then the comm column remains and all the expected events are present.

This patch prevents filtered out events from being considered by
hist_entry_iter__add.

Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Steve Capper <steve.capper@xxxxxxxxxx>
---
Hi,
This patch fixes my problem, but I don't know enough perf to
confidently state that this will work everywhere (hence this being
marked as an RFC).

Please let me know if I've missed something and I'll be happy to
re-spin/test/submit.

Cheers,
-- 
Steve
---
 tools/perf/builtin-report.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 2f91094..3eaf46e 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -166,6 +166,9 @@ static int process_sample_event(struct perf_tool *tool,
 	if (al.map != NULL)
 		al.map->dso->hit = 1;
 
+	if (al.filtered)
+		return 0;
+
 	ret = hist_entry_iter__add(&iter, &al, evsel, sample, rep->max_stack,
 				   rep);
 	if (ret < 0)
-- 
2.1.0

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