[PATCH 06/17] perf evsel: Add comment for 'idx' member in 'struct perf_sample_id

From: Arnaldo Carvalho de Melo
Date: Tue Aug 20 2019 - 15:28:18 EST

From: Adrian Hunter <adrian.hunter@xxxxxxxxx>

The 'idx' member was added as preparation for AUX area sampling. Add a
comment to describe why.

Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Michael Petlan <mpetlan@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/83ff264f-84c3-5372-8976-dd9293d20c6f@xxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
tools/perf/util/evsel.h | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 9cd6e3ae479a..efe08065838f 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -23,6 +23,13 @@ struct perf_sample_id {
struct hlist_node node;
u64 id;
struct evsel *evsel;
+ /*
+ * 'idx' will be used for AUX area sampling. A sample will have AUX area
+ * data that will be queued for decoding, where there are separate
+ * queues for each CPU (per-cpu tracing) or task (per-thread tracing).
+ * The sample ID can be used to lookup 'idx' which is effectively the
+ * queue number.
+ */
int idx;
int cpu;
pid_t tid;