[PATCH v3 2/7] perf util: Create streams for managing top N hottest callchains

[Jin Yao]

We think the stream is a callchain which is aggregated by the LBR
records from samples. By browsing the stream, we can understand
the code flow.

The struct callchain_node represents one callchain and we use the
callchain_node->hit to measure the hot level of this callchain.
Higher is hotter.

Since in perf data file, there may be many callchains so we just
need to focus on the top N hottest callchains. N is a user defined
parameter or just a predefined default value.

This patch saves the top N hottest callchains in 'struct stream_node'
type array, which is defined in a per event 'struct callchain_streams'.

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

 v2:
 ---
 Use zfree in free_evsel_streams().

Signed-off-by: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
---
 tools/perf/util/callchain.c | 122 ++++++++++++++++++++++++++++++++++++
 tools/perf/util/callchain.h |  16 +++++
 2 files changed, 138 insertions(+)

diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
index 818aa4efd386..0c028caaeb19 100644
--- a/tools/perf/util/callchain.c
+++ b/tools/perf/util/callchain.c
@@ -31,6 +31,7 @@
 #include "callchain.h"
 #include "branch.h"
 #include "symbol.h"
+#include "evlist.h"
 #include "../perf.h"
 
 #define CALLCHAIN_PARAM_DEFAULT			\
@@ -1599,3 +1600,124 @@ void callchain_cursor_reset(struct callchain_cursor *cursor)
 	for (node = cursor->first; node != NULL; node = node->next)
 		map__zput(node->ms.map);
 }
+
+static void free_evsel_streams(struct callchain_streams *callchain_streams,
+			       int nr_evsel)
+{
+	for (int i = 0; i < nr_evsel; i++)
+		zfree(&callchain_streams[i].streams);
+
+	free(callchain_streams);
+}
+
+static struct callchain_streams *create_evsel_streams(int nr_evsel,
+						      int nr_streams_max)
+{
+	struct callchain_streams *callchain_streams;
+
+	callchain_streams = calloc(nr_evsel, sizeof(struct callchain_streams));
+	if (!callchain_streams)
+		return NULL;
+
+	for (int i = 0; i < nr_evsel; i++) {
+		struct callchain_streams *s = &callchain_streams[i];
+
+		s->streams = calloc(nr_streams_max, sizeof(struct stream_node));
+		if (!s->streams)
+			goto err;
+
+		s->nr_streams_max = nr_streams_max;
+		s->evsel_idx = -1;
+	}
+
+	return callchain_streams;
+
+err:
+	free_evsel_streams(callchain_streams, nr_evsel);
+	return NULL;
+}
+
+/*
+ * The cnodes with high hit number are hot callchains.
+ */
+static void set_hot_cnode(struct callchain_streams *s,
+			  struct callchain_node *cnode)
+{
+	int i, idx = 0;
+	u64 hit;
+
+	if (s->nr_streams < s->nr_streams_max) {
+		i = s->nr_streams;
+		s->streams[i].cnode = cnode;
+		s->nr_streams++;
+		return;
+	}
+
+	/*
+	 * Since only a few number of hot streams, so only use simple
+	 * way to find the cnode with smallest hit number and replace.
+	 */
+	hit = (s->streams[0].cnode)->hit;
+	for (i = 1; i < s->nr_streams; i++) {
+		if ((s->streams[i].cnode)->hit < hit) {
+			hit = (s->streams[i].cnode)->hit;
+			idx = i;
+		}
+	}
+
+	if (cnode->hit > hit)
+		s->streams[idx].cnode = cnode;
+}
+
+static void update_hot_streams(struct hist_entry *he,
+			       struct callchain_streams *s)
+{
+	struct rb_root *root = &he->sorted_chain;
+	struct rb_node *rb_node = rb_first(root);
+	struct callchain_node *node;
+
+	while (rb_node) {
+		node = rb_entry(rb_node, struct callchain_node, rb_node);
+		set_hot_cnode(s, node);
+		rb_node = rb_next(rb_node);
+	}
+}
+
+static void get_hot_streams(struct hists *hists,
+			    struct callchain_streams *s)
+{
+	struct rb_node *next = rb_first_cached(&hists->entries);
+
+	while (next) {
+		struct hist_entry *he;
+
+		he = rb_entry(next, struct hist_entry, rb_node);
+		update_hot_streams(he, s);
+		next = rb_next(&he->rb_node);
+	}
+}
+
+struct callchain_streams *callchain_evsel_streams_create(struct evlist *evlist,
+							 int nr_streams_max,
+							 int *nr_evsel_streams)
+{
+	int nr_evsel = evlist->core.nr_entries, i = 0;
+	struct callchain_streams *callchain_streams;
+	struct evsel *pos;
+
+	callchain_streams = create_evsel_streams(nr_evsel, nr_streams_max);
+	if (!callchain_streams)
+		return NULL;
+
+	evlist__for_each_entry(evlist, pos) {
+		struct hists *hists = evsel__hists(pos);
+
+		hists__output_resort(hists, NULL);
+		get_hot_streams(hists, &callchain_streams[i]);
+		callchain_streams[i].evsel_idx = pos->idx;
+		i++;
+	}
+
+	*nr_evsel_streams = nr_evsel;
+	return callchain_streams;
+}
diff --git a/tools/perf/util/callchain.h b/tools/perf/util/callchain.h
index 8f668ee29f25..6a93ad84d395 100644
--- a/tools/perf/util/callchain.h
+++ b/tools/perf/util/callchain.h
@@ -13,6 +13,7 @@ struct ip_callchain;
 struct map;
 struct perf_sample;
 struct thread;
+struct evlist;
 
 #define HELP_PAD "\t\t\t\t"
 
@@ -167,6 +168,17 @@ struct callchain_cursor {
 	struct callchain_cursor_node	*curr;
 };
 
+struct stream_node {
+	struct callchain_node	*cnode;
+};
+
+struct callchain_streams {
+	struct stream_node	*streams;
+	int			nr_streams_max;
+	int			nr_streams;
+	int			evsel_idx;
+};
+
 extern __thread struct callchain_cursor callchain_cursor;
 
 static inline void callchain_init(struct callchain_root *root)
@@ -297,4 +309,8 @@ int callchain_branch_counts(struct callchain_root *root,
 			    u64 *branch_count, u64 *predicted_count,
 			    u64 *abort_count, u64 *cycles_count);
 
+struct callchain_streams *callchain_evsel_streams_create(struct evlist *evlist,
+							 int nr_streams_max,
+							 int *nr_evsel_streams);
+
 #endif	/* __PERF_CALLCHAIN_H */
-- 
2.17.1