[PATCH v4 2/9] perf ui hist: Add support for aggregated total_period and merging entries

[Ian Rogers <irogers@google.com>]

Add the histogram side of hybrid event merging.

When events are merged the entries of the other events are linked to
the leader's entries as pairs, and a row is then displayed as the sum
over an entry and its pairs. Teach the hpp code to work on that sum:

 - The formatting and sorting routines add up the value of an entry and
   of each of its pairs, so a row shows, and is sorted by, the total
   across the core PMUs rather than the leader's value alone.
 - Percentages are taken against the summed total_period of the merged
   hists. Computing each event's share against its own PMU's total
   would leave the column not adding up to 100%.
   hist_entry__get_percent_limit_merged() does the same for
   --percent-limit, which would otherwise compare against the wrong
   total and filter out the wrong entries.
 - A header and column width are reserved for the "Total" the merged
   value is shown under.

evlist__merge_hists_hybrid() links the hists together and resorts the
result so that it is ordered by the merged total.

hists__link() is run once for every event merged into the leader, so an
entry can be offered as a pair more than once. hist_entry__add_pair()
used list_add_tail() unconditionally, which corrupts the list when the
entry is already on one. Return early if the entry is already paired
with this one, and use list_move_tail() so that an entry linked
elsewhere is moved rather than added a second time.

Merging is never combined with --hierarchy, which the merge_entries
tests rely on.

Signed-off-by: Ian Rogers <irogers@google.com>
Assisted-by: Antigravity:gemini-3.1-pro
---
 tools/perf/ui/hist.c   | 246 +++++++++++++++++++++++++++++++++++++++--
 tools/perf/util/hist.h |  14 ++-
 2 files changed, 252 insertions(+), 8 deletions(-)

diff --git a/tools/perf/ui/hist.c b/tools/perf/ui/hist.c
index e58327595d37..09da45c80889 100644
--- a/tools/perf/ui/hist.c
+++ b/tools/perf/ui/hist.c
@@ -57,8 +57,9 @@ struct hpp_fmt_value {
 };
 
 static int __hpp__fmt(struct perf_hpp *hpp, struct hist_entry *he,
-		      hpp_field_fn get_field, const char *fmt, int len,
-		      hpp_snprint_fn print_fn, enum perf_hpp_fmt_type fmtype)
+		      hpp_field_fn get_field, const char *fmtstr, int len,
+		      hpp_snprint_fn print_fn, enum perf_hpp_fmt_type fmtype,
+		      struct perf_hpp_fmt *fmt __maybe_unused)
 {
 	int ret = 0;
 	struct hists *hists = he->hists;
@@ -98,13 +99,50 @@ static int __hpp__fmt(struct perf_hpp *hpp, struct hist_entry *he,
 		}
 	}
 
+	/* Note, merge_entries implies !symbol_conf.report_hierarchy. */
+	if (he->hists->merge_entries) {
+		u64 total_val = 0;
+		u64 total_samples = 0;
+		u64 total_period = 0;
+
+		for (i = 0; i < nr_members; i++) {
+			struct evsel *member_evsel = hists_to_evsel(values[i].hists);
+
+			struct evsel *he_evsel = hists_to_evsel(he->hists);
+
+			if (member_evsel != he_evsel &&
+			    member_evsel->first_wildcard_match != he_evsel)
+				continue;
+
+			total_val += values[i].val;
+			total_samples += values[i].samples;
+			total_period += fmtype == PERF_HPP_FMT_TYPE__PERCENT ?
+					hists__total_period(values[i].hists) :
+					hists__total_latency(values[i].hists);
+		}
+
+		if (fmtype == PERF_HPP_FMT_TYPE__PERCENT || fmtype == PERF_HPP_FMT_TYPE__LATENCY) {
+			double percent = 0.0;
+
+			if (total_period)
+				percent = 100.0 * total_val / total_period;
+			ret += hpp__call_print_fn(hpp, print_fn, fmtstr, len, percent);
+		} else if (fmtype == PERF_HPP_FMT_TYPE__AVERAGE) {
+			double avg = total_samples ? (1.0 * total_val / total_samples) : 0;
+
+			ret += hpp__call_print_fn(hpp, print_fn, fmtstr, len, avg);
+		} else {
+			ret += hpp__call_print_fn(hpp, print_fn, fmtstr, len, total_val);
+		}
+	}
+
 	for (i = 0; i < nr_members; i++) {
 		if (symbol_conf.skip_empty &&
 		    values[i].hists->stats.nr_samples == 0)
 			continue;
 
 		ret += __hpp__fmt_print(hpp, values[i].hists, values[i].val,
-					values[i].samples, fmt, len,
+					values[i].samples, fmtstr, len,
 					print_fn, fmtype);
 	}
 
@@ -129,7 +167,7 @@ int hpp__fmt(struct perf_hpp_fmt *fmt, struct perf_hpp *hpp,
 
 	if (symbol_conf.field_sep) {
 		return __hpp__fmt(hpp, he, get_field, fmtstr, 1,
-				  print_fn, fmtype);
+				  print_fn, fmtype, fmt);
 	}
 
 	if (fmtype == PERF_HPP_FMT_TYPE__PERCENT || fmtype == PERF_HPP_FMT_TYPE__LATENCY)
@@ -137,7 +175,7 @@ int hpp__fmt(struct perf_hpp_fmt *fmt, struct perf_hpp *hpp,
 	else
 		len -= 1;
 
-	return  __hpp__fmt(hpp, he, get_field, fmtstr, len, print_fn, fmtype);
+	return  __hpp__fmt(hpp, he, get_field, fmtstr, len, print_fn, fmtype, fmt);
 }
 
 int hpp__fmt_acc(struct perf_hpp_fmt *fmt, struct perf_hpp *hpp,
@@ -287,6 +325,35 @@ static int __hpp__sort(struct hist_entry *a, struct hist_entry *b,
 		return __hpp__group_sort_idx(a, b, get_field,
 					     symbol_conf.group_sort_idx);
 	}
+	/*
+	 * Relies on merge_entries being only enabled if there are
+	 * only matching events. If that is ever relaxed will need
+	 * more logic here. merge_entries also implies that
+	 * symbol_conf.report_hierarchy is false.
+	 */
+	if (a->hists->merge_entries && b->hists->merge_entries) {
+		u64 val_a = get_field(a), val_b = get_field(b);
+		struct hist_entry *pair;
+		struct evsel *evsel_a = hists_to_evsel(a->hists);
+		struct evsel *evsel_b = hists_to_evsel(b->hists);
+
+		list_for_each_entry(pair, &a->pairs.head, pairs.node) {
+			struct evsel *pair_evsel = hists_to_evsel(pair->hists);
+
+			if (pair_evsel->first_wildcard_match == evsel_a)
+				val_a += get_field(pair);
+		}
+		list_for_each_entry(pair, &b->pairs.head, pairs.node) {
+			struct evsel *pair_evsel = hists_to_evsel(pair->hists);
+
+			if (pair_evsel->first_wildcard_match == evsel_b)
+				val_b += get_field(pair);
+		}
+
+		ret = field_cmp(val_a, val_b);
+		if (ret)
+			return ret;
+	}
 
 	ret = field_cmp(get_field(a), get_field(b));
 	if (ret || !symbol_conf.event_group)
@@ -323,7 +390,29 @@ static int __hpp__sort_acc(struct hist_entry *a, struct hist_entry *b,
 		/*
 		 * Put caller above callee when they have equal period.
 		 */
-		ret = field_cmp(get_field(a), get_field(b));
+		if (a->hists->merge_entries && b->hists->merge_entries) {
+			u64 val_a = get_field(a), val_b = get_field(b);
+			struct hist_entry *pair;
+			struct evsel *evsel_a = hists_to_evsel(a->hists);
+			struct evsel *evsel_b = hists_to_evsel(b->hists);
+
+			list_for_each_entry(pair, &a->pairs.head, pairs.node) {
+				struct evsel *pair_evsel = hists_to_evsel(pair->hists);
+
+				if (pair_evsel->first_wildcard_match == evsel_a)
+					val_a += get_field(pair);
+			}
+			list_for_each_entry(pair, &b->pairs.head, pairs.node) {
+				struct evsel *pair_evsel = hists_to_evsel(pair->hists);
+
+				if (pair_evsel->first_wildcard_match == evsel_b)
+					val_b += get_field(pair);
+			}
+
+			ret = field_cmp(val_a, val_b);
+		} else {
+			ret = field_cmp(get_field(a), get_field(b));
+		}
 		if (ret)
 			return ret;
 
@@ -386,6 +475,8 @@ static int hpp__width_fn(struct perf_hpp_fmt *fmt,
 			    evsel__hists(pos)->stats.nr_samples)
 				nr++;
 		}
+		if (hists->merge_entries)
+			nr++; /* Add 1 extra unit of width generically for the 'Total' */
 
 		len = max(len, nr * fmt->len);
 	}
@@ -403,8 +494,38 @@ static int hpp__header_fn(struct perf_hpp_fmt *fmt, struct perf_hpp *hpp,
 	int len = hpp__width_fn(fmt, hpp, hists);
 	const char *hdr = "";
 
-	if (line == hists->hpp_list->nr_header_lines - 1)
+	if (line == hists->hpp_list->nr_header_lines - 1) {
 		hdr = fmt->name;
+		if (hists->merge_entries) {
+			int w = 0;
+			int f_len = fmt->user_len ?: fmt->len;
+			struct evsel *pos, *evsel = hists_to_evsel(hists);
+			int string_len = f_len;
+
+			for_each_group_evsel(pos, evsel) {
+				if (symbol_conf.skip_empty &&
+				    evsel__hists(pos)->stats.nr_samples == 0)
+					continue;
+				string_len += f_len;
+			}
+
+			if (len > string_len) {
+				w += scnprintf(hpp->buf + w, hpp->size - w, "%*s",
+					       len - string_len, "");
+			}
+
+			w += scnprintf(hpp->buf + w, hpp->size - w, "%*.*s",
+				       f_len, f_len, fmt->name);
+			for_each_group_evsel(pos, evsel) {
+				if (symbol_conf.skip_empty &&
+				    evsel__hists(pos)->stats.nr_samples == 0)
+					continue;
+				w += scnprintf(hpp->buf + w, hpp->size - w, " %*.*s",
+					       f_len - 1, f_len - 1, evsel__name(pos));
+			}
+			return w;
+		}
+	}
 
 	return scnprintf(hpp->buf, hpp->size, "%*s", len, hdr);
 }
@@ -1271,3 +1392,114 @@ int perf_hpp__alloc_mem_stats(struct perf_hpp_list *list, struct evlist *evlist)
 	}
 	return 0;
 }
+
+float hist_entry__get_percent_limit_merged(struct hist_entry *he)
+{
+	struct hist_entry *pair;
+	u64 period = he->stat.period;
+	u64 total_period = hists__total_period(he->hists);
+	struct evsel *evsel = hists_to_evsel(he->hists);
+	struct evsel *pos;
+
+	/* Accumulate global total_period across all merged hists matching hybrid type */
+	for_each_group_member(pos, evsel) {
+		if (pos->first_wildcard_match == evsel)
+			total_period += hists__total_period(evsel__hists(pos));
+	}
+
+	if (unlikely(total_period == 0))
+		return 0;
+
+	if (symbol_conf.cumulate_callchain) {
+		period = he->stat_acc->period;
+		list_for_each_entry(pair, &he->pairs.head, pairs.node) {
+			struct evsel *pair_evsel = hists_to_evsel(pair->hists);
+
+			if (pair_evsel->first_wildcard_match == evsel)
+				period += pair->stat_acc->period;
+		}
+	} else {
+		/* Accumulate symbol specific period across pairs matching hybrid type */
+		list_for_each_entry(pair, &he->pairs.head, pairs.node) {
+			struct evsel *pair_evsel = hists_to_evsel(pair->hists);
+
+			if (pair_evsel->first_wildcard_match == evsel)
+				period += pair->stat.period;
+		}
+	}
+
+	return period * 100.0 / total_period;
+}
+
+void evlist__merge_hists_hybrid(struct evlist *evlist, bool refresh_hists)
+{
+	struct evsel *pos;
+	struct evsel *member;
+	bool hybrid_group;
+
+	/*
+	 * Merged hists display all the events of a group in a single set of
+	 * entries, which the hierarchy display has no way to render. Keeping
+	 * hists->merge_entries false here means the rest of the display code
+	 * can assume merge_entries implies !symbol_conf.report_hierarchy.
+	 */
+	if (symbol_conf.report_hierarchy)
+		return;
+
+	/* Set merge_entries flag strictly on leaders formulated by hybrid topology */
+	evlist__for_each_entry(evlist, pos) {
+		if (evsel__is_dummy_event(pos))
+			continue;
+
+		if (pos->core.leader == &pos->core && pos->core.nr_members > 1) {
+			hybrid_group = false;
+
+			if (pos->first_wildcard_match || pos->merged_hybrid_group) {
+				hybrid_group = true;
+			} else {
+				for_each_group_member(member, pos) {
+					if (member->first_wildcard_match ||
+					    member->merged_hybrid_group) {
+						hybrid_group = true;
+						break;
+					}
+				}
+			}
+
+			if (hybrid_group) {
+				evsel__hists(pos)->merge_entries = true;
+				symbol_conf.event_group = true;
+				symbol_conf.hybrid_merge = true;
+				if (!pos->group_name) {
+					pos->group_name = strdup("Merged hybrid events");
+					if (!pos->group_name)
+						pr_warning("Failed to allocate hybrid group name\n");
+				}
+			}
+		}
+	}
+
+	if (!refresh_hists)
+		return;
+
+	evlist__for_each_entry(evlist, pos) {
+		/* Match histograms dynamically since parsing happened before group toggling */
+		if (symbol_conf.event_group && !evsel__is_group_leader(pos)) {
+			struct hists *leader_hists = evsel__hists(evsel__leader(pos));
+			struct hists *hists = evsel__hists(pos);
+
+			hists__match(leader_hists, hists);
+			hists__link(leader_hists, hists);
+		}
+	}
+
+	/* Now that links are formed, safely resort the active tree so the UI renders accurately */
+	if (symbol_conf.event_group) {
+		evlist__for_each_entry(evlist, pos) {
+			if (evsel__is_dummy_event(pos) || !evsel__is_group_leader(pos))
+				continue;
+			if (pos->core.nr_members > 1 && evsel__hists(pos)->merge_entries)
+				hists__output_resort(evsel__hists(pos), NULL);
+		}
+	}
+}
diff --git a/tools/perf/util/hist.h b/tools/perf/util/hist.h
index d0ed43807cf6..0d08011aebce 100644
--- a/tools/perf/util/hist.h
+++ b/tools/perf/util/hist.h
@@ -339,7 +339,13 @@ static inline struct hist_entry *hist_entry__next_pair(struct hist_entry *he)
 static inline void hist_entry__add_pair(struct hist_entry *pair,
 					struct hist_entry *he)
 {
-	list_add_tail(&pair->pairs.node, &he->pairs.head);
+	struct list_head *pos;
+
+	list_for_each(pos, &he->pairs.head) {
+		if (pos == &pair->pairs.node)
+			return; /* Already paired */
+	}
+	list_move_tail(&pair->pairs.node, &he->pairs.head);
 }
 
 struct hist_entry *hists__add_entry(struct hists *hists,
@@ -434,11 +440,17 @@ void hists__match(struct hists *leader, struct hists *other);
 int hists__link(struct hists *leader, struct hists *other);
 int hists__unlink(struct hists *hists);
 
+float hist_entry__get_percent_limit_merged(struct hist_entry *he);
+void evlist__merge_hists_hybrid(struct evlist *evlist, bool refresh);
+
 static inline float hist_entry__get_percent_limit(struct hist_entry *he)
 {
 	u64 period = he->stat.period;
 	u64 total_period = hists__total_period(he->hists);
 
+	if (he->hists->merge_entries)
+		return hist_entry__get_percent_limit_merged(he);
+
 	if (unlikely(total_period == 0))
 		return 0;
 
-- 
2.55.0.1082.g2b9226bbc0-goog