perf diff: Start moving to support matching more than two hists

We want to match more than two hists, so that we can match more than two
perf.data files and moreover, match hist_entries (buckets) in multiple
events in a group.

So the "baseline"/"leader" will instead of a ->pair pointer, use a
list_head, that will link to the pairs and hists__match use it.

Following that perf_evlist__link will link the hists in its evsel
groups.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-2kbmzepoi544ygj9godseqpv@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-diff.c

@@ -154,7 +154,7 @@ static double get_period_percent(struct hist_entry *he, u64 period)
 
 double perf_diff__compute_delta(struct hist_entry *he)
 {
-	struct hist_entry *pair = he->pair;
+	struct hist_entry *pair = hist_entry__next_pair(he);
 	double new_percent = get_period_percent(he, he->stat.period);
 	double old_percent = pair ? get_period_percent(pair, pair->stat.period) : 0.0;
 
@@ -165,7 +165,7 @@ double perf_diff__compute_delta(struct hist_entry *he)
 
 double perf_diff__compute_ratio(struct hist_entry *he)
 {
-	struct hist_entry *pair = he->pair;
+	struct hist_entry *pair = hist_entry__next_pair(he);
 	double new_period = he->stat.period;
 	double old_period = pair ? pair->stat.period : 0;
 
@@ -176,7 +176,7 @@ double perf_diff__compute_ratio(struct hist_entry *he)
 
 s64 perf_diff__compute_wdiff(struct hist_entry *he)
 {
-	struct hist_entry *pair = he->pair;
+	struct hist_entry *pair = hist_entry__next_pair(he);
 	u64 new_period = he->stat.period;
 	u64 old_period = pair ? pair->stat.period : 0;
 
@@ -193,7 +193,7 @@ s64 perf_diff__compute_wdiff(struct hist_entry *he)
 
 static int formula_delta(struct hist_entry *he, char *buf, size_t size)
 {
-	struct hist_entry *pair = he->pair;
+	struct hist_entry *pair = hist_entry__next_pair(he);
 
 	if (!pair)
 		return -1;
@@ -207,7 +207,7 @@ static int formula_delta(struct hist_entry *he, char *buf, size_t size)
 
 static int formula_ratio(struct hist_entry *he, char *buf, size_t size)
 {
-	struct hist_entry *pair = he->pair;
+	struct hist_entry *pair = hist_entry__next_pair(he);
 	double new_period = he->stat.period;
 	double old_period = pair ? pair->stat.period : 0;
 
@@ -219,7 +219,7 @@ static int formula_ratio(struct hist_entry *he, char *buf, size_t size)
 
 static int formula_wdiff(struct hist_entry *he, char *buf, size_t size)
 {
-	struct hist_entry *pair = he->pair;
+	struct hist_entry *pair = hist_entry__next_pair(he);
 	u64 new_period = he->stat.period;
 	u64 old_period = pair ? pair->stat.period : 0;
 
@@ -359,8 +359,11 @@ static void hists__match(struct hists *older, struct hists *newer)
 	struct rb_node *nd;
 
 	for (nd = rb_first(&newer->entries); nd; nd = rb_next(nd)) {
-		struct hist_entry *pos = rb_entry(nd, struct hist_entry, rb_node);
-		pos->pair = hists__find_entry(older, pos);
+		struct hist_entry *pos = rb_entry(nd, struct hist_entry, rb_node),
+				  *pair = hists__find_entry(older, pos);
+
+		if (pair)
+			hist__entry_add_pair(pos, pair);
 	}
 }
 
@@ -402,7 +405,7 @@ static void hists__baseline_only(struct hists *hists)
 		struct hist_entry *he = rb_entry(next, struct hist_entry, rb_node);
 
 		next = rb_next(&he->rb_node);
-		if (!he->pair) {
+		if (!hist_entry__next_pair(he)) {
 			rb_erase(&he->rb_node, &hists->entries);
 			hist_entry__free(he);
 		}

tools/perf/ui/hist.c

@@ -161,7 +161,7 @@ static int hpp__width_baseline(struct perf_hpp *hpp __maybe_unused)
 
 static double baseline_percent(struct hist_entry *he)
 {
-	struct hist_entry *pair = he->pair;
+	struct hist_entry *pair = hist_entry__next_pair(he);
 	struct hists *pair_hists = pair ? pair->hists : NULL;
 	double percent = 0.0;
 
@@ -179,7 +179,7 @@ static int hpp__color_baseline(struct perf_hpp *hpp, struct hist_entry *he)
 {
 	double percent = baseline_percent(he);
 
-	if (he->pair)
+	if (hist_entry__has_pairs(he))
 		return percent_color_snprintf(hpp->buf, hpp->size, " %6.2f%%", percent);
 	else
 		return scnprintf(hpp->buf, hpp->size, "        ");
@@ -190,7 +190,7 @@ static int hpp__entry_baseline(struct perf_hpp *hpp, struct hist_entry *he)
 	double percent = baseline_percent(he);
 	const char *fmt = symbol_conf.field_sep ? "%.2f" : " %6.2f%%";
 
-	if (he->pair || symbol_conf.field_sep)
+	if (hist_entry__has_pairs(he) || symbol_conf.field_sep)
 		return scnprintf(hpp->buf, hpp->size, fmt, percent);
 	else
 		return scnprintf(hpp->buf, hpp->size, "            ");
@@ -248,7 +248,7 @@ static int hpp__width_period_baseline(struct perf_hpp *hpp __maybe_unused)
 
 static int hpp__entry_period_baseline(struct perf_hpp *hpp, struct hist_entry *he)
 {
-	struct hist_entry *pair = he->pair;
+	struct hist_entry *pair = hist_entry__next_pair(he);
 	u64 period = pair ? pair->stat.period : 0;
 	const char *fmt = symbol_conf.field_sep ? "%" PRIu64 : "%12" PRIu64;
 
@@ -354,7 +354,7 @@ static int hpp__width_displ(struct perf_hpp *hpp __maybe_unused)
 static int hpp__entry_displ(struct perf_hpp *hpp,
 			    struct hist_entry *he)
 {
-	struct hist_entry *pair = he->pair;
+	struct hist_entry *pair = hist_entry__next_pair(he);
 	long displacement = pair ? pair->position - he->position : 0;
 	const char *fmt = symbol_conf.field_sep ? "%s" : "%6.6s";
 	char buf[32] = " ";

tools/perf/util/hist.c

@@ -244,6 +244,8 @@ static struct hist_entry *hist_entry__new(struct hist_entry *template)
 			he->ms.map->referenced = true;
 		if (symbol_conf.use_callchain)
 			callchain_init(he->callchain);
+
+		INIT_LIST_HEAD(&he->pairs.node);
 	}
 
 	return he;

tools/perf/util/sort.h

@@ -77,6 +77,10 @@ struct hist_entry_diff {
 struct hist_entry {
 	struct rb_node		rb_node_in;
 	struct rb_node		rb_node;
+	union {
+		struct list_head node;
+		struct list_head head;
+	} pairs;
 	struct he_stat		stat;
 	struct map_symbol	ms;
 	struct thread		*thread;
@@ -96,15 +100,30 @@ struct hist_entry {
 	char			*srcline;
 	struct symbol		*parent;
 	unsigned long		position;
-	union {
-		struct hist_entry *pair;
-		struct rb_root	  sorted_chain;
-	};
+	struct rb_root		sorted_chain;
 	struct branch_info	*branch_info;
 	struct hists		*hists;
 	struct callchain_root	callchain[0];
 };
 
+static inline bool hist_entry__has_pairs(struct hist_entry *he)
+{
+	return !list_empty(&he->pairs.node);
+}
+
+static inline struct hist_entry *hist_entry__next_pair(struct hist_entry *he)
+{
+	if (hist_entry__has_pairs(he))
+		return list_entry(he->pairs.node.next, struct hist_entry, pairs.node);
+	return NULL;
+}
+
+static inline void hist__entry_add_pair(struct hist_entry *he,
+					struct hist_entry *pair)
+{
+	list_add_tail(&he->pairs.head, &pair->pairs.node);
+}
+
 enum sort_type {
 	SORT_PID,
 	SORT_COMM,