perf streams: Introduce branch history "streams"

We define a stream as the branch history which is aggregated by the
branch records from perf samples. For example, the callchains aggregated
from the branch records are considered as streams.  By browsing the hot
stream, we can understand the hot code path.

Now we only support the callchain for stream. For measuring the hot
level for a stream, we use the callchain_node->hit, higher is hotter.

There may be many callchains sampled so we only focus on the top N
hottest callchains. N is a user defined parameter or predefined default
value (nr_streams_max).

This patch creates an evsel_streams array per event, and saves the top N
hottest streams in a stream array.

So now we can get the per-event top N hottest streams.

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20201009022845.13141-2-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/tools/perf/util/stream.h b/tools/perf/util/stream.h
new file mode 100644
index 000000000000..35bc64df554c
--- /dev/null
+++ b/tools/perf/util/stream.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PERF_STREAM_H
+#define __PERF_STREAM_H
+
+#include "callchain.h"
+
+struct stream {
+	struct callchain_node	*cnode;
+};
+
+struct evsel_streams {
+	struct stream		*streams;
+	int			nr_streams_max;
+	int			nr_streams;
+	int			evsel_idx;
+};
+
+struct evlist_streams {
+	struct evsel_streams	*ev_streams;
+	int			nr_evsel;
+};
+
+struct evlist;
+
+void evlist_streams__delete(struct evlist_streams *els);
+
+struct evlist_streams *evlist__create_streams(struct evlist *evlist,
+					      int nr_streams_max);
+
+#endif /* __PERF_STREAM_H */