perf stat: Save aggr value to first member of prev_raw_counts

To collect the overall statistics for interval mode, we copy the counts
from evsel->prev_raw_counts to evsel->counts.

For AGGR_GLOBAL mode, because the perf_stat_process_counter creates aggr
values from per cpu values, but the per cpu values are 0, so the
calculated aggr values will be always 0.

This patch uses a trick that saves the previous aggr value to the first
member of perf_counts, then aggr calculation in process_counter_values
can work correctly for AGGR_GLOBAL.

 v6:
 ---
 Add comments in perf_evlist__save_aggr_prev_raw_counts.
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200520042737.24160-5-yao.jin@linux.intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/stat.c

@@ -249,6 +249,26 @@ void perf_evlist__copy_prev_raw_counts(struct evlist *evlist)
 		perf_evsel__copy_prev_raw_counts(evsel);
 }
 
+void perf_evlist__save_aggr_prev_raw_counts(struct evlist *evlist)
+{
+	struct evsel *evsel;
+
+	/*
+	 * To collect the overall statistics for interval mode,
+	 * we copy the counts from evsel->prev_raw_counts to
+	 * evsel->counts. The perf_stat_process_counter creates
+	 * aggr values from per cpu values, but the per cpu values
+	 * are 0 for AGGR_GLOBAL. So we use a trick that saves the
+	 * previous aggr value to the first member of perf_counts,
+	 * then aggr calculation in process_counter_values can work
+	 * correctly.
+	 */
+	evlist__for_each_entry(evlist, evsel) {
+		*perf_counts(evsel->prev_raw_counts, 0, 0) =
+			evsel->prev_raw_counts->aggr;
+	}
+}
+
 static void zero_per_pkg(struct evsel *counter)
 {
 	if (counter->per_pkg_mask)

tools/perf/util/stat.h

@@ -199,6 +199,7 @@ void perf_evlist__free_stats(struct evlist *evlist);
 void perf_evlist__reset_stats(struct evlist *evlist);
 void perf_evlist__reset_prev_raw_counts(struct evlist *evlist);
 void perf_evlist__copy_prev_raw_counts(struct evlist *evlist);
+void perf_evlist__save_aggr_prev_raw_counts(struct evlist *evlist);
 
 int perf_stat_process_counter(struct perf_stat_config *config,
 			      struct evsel *counter);