1 files changed, 14 insertions, 2 deletions

diff --git a/tools/perf/util/hist.h b/tools/perf/util/hist.h
index 97b8962ff69a..da6b84814a50 100644
--- a/tools/perf/util/hist.h
+++ b/tools/perf/util/hist.h
@@ -37,9 +37,21 @@ struct sym_priv {
         struct sym_ext  *ext;
 };
 
+/*
+ * The kernel collects the number of events it couldn't send in a stretch and
+ * when possible sends this number in a PERF_RECORD_LOST event. The number of
+ * such "chunks" of lost events is stored in .nr_events[PERF_EVENT_LOST] while
+ * total_lost tells exactly how many events the kernel in fact lost, i.e. it is
+ * the sum of all struct lost_event.lost fields reported.
+ *
+ * The total_period is needed because by default auto-freq is used, so
+ * multipling nr_events[PERF_EVENT_SAMPLE] by a frequency isn't possible to get
+ * the total number of low level events, it is necessary to to sum all struct
+ * sample_event.period and stash the result in total_period.
+ */
 struct events_stats {
-        u64 total;
-        u64 lost;
+        u64 total_period;
+        u64 total_lost;
         u32 nr_events[PERF_RECORD_HEADER_MAX];
         u32 nr_unknown_events;
 };