perf maps: Add/use a sorted insert for fixup overlap and insert

Data may have lots of overlapping mmaps. The regular insert adds at
the end and relies on a later sort. For data with overlapping mappings
the sort will happen during a subsequent maps__find or
__maps__fixup_overlap_and_insert, there's never a period where the
inserted maps buffer up and a single sort happens. To avoid back to
back sorts, maintain the sort order when fixing up and
inserting. Previously the first_ending_after search was O(log n) where
n is the size of maps, and the insert was O(1) but because of the
continuous sorting was becoming O(n*log(n)). With maintaining sort
order, the insert now becomes O(n) for a memmove.

For a perf report on a perf.data file containing overlapping mappings
the time numbers are:

Before:
real    0m5.894s
user    0m5.650s
sys     0m0.231s

After:
real    0m0.675s
user    0m0.454s
sys     0m0.196s
Signed-off-by: Ian Rogers <irogers@google.com>
Reviewed-by: James Clark <james.clark@arm.com>
Cc: Steinar H . Gunderson <sesse@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240521165109.708593-4-irogers@google.com

tools/perf/util/maps.c

@@ -735,6 +735,60 @@ static unsigned int first_ending_after(struct maps *maps, const struct map *map)
 	return first;
 }
 
+static int __maps__insert_sorted(struct maps *maps, unsigned int first_after_index,
+				 struct map *new1, struct map *new2)
+{
+	struct map **maps_by_address = maps__maps_by_address(maps);
+	struct map **maps_by_name = maps__maps_by_name(maps);
+	unsigned int nr_maps = maps__nr_maps(maps);
+	unsigned int nr_allocate = RC_CHK_ACCESS(maps)->nr_maps_allocated;
+	unsigned int to_add = new2 ? 2 : 1;
+
+	assert(maps__maps_by_address_sorted(maps));
+	assert(first_after_index == nr_maps ||
+	       map__end(new1) <= map__start(maps_by_address[first_after_index]));
+	assert(!new2 || map__end(new1) <= map__start(new2));
+	assert(first_after_index == nr_maps || !new2 ||
+	       map__end(new2) <= map__start(maps_by_address[first_after_index]));
+
+	if (nr_maps + to_add > nr_allocate) {
+		nr_allocate = !nr_allocate ? 32 : nr_allocate * 2;
+
+		maps_by_address = realloc(maps_by_address, nr_allocate * sizeof(new1));
+		if (!maps_by_address)
+			return -ENOMEM;
+
+		maps__set_maps_by_address(maps, maps_by_address);
+		if (maps_by_name) {
+			maps_by_name = realloc(maps_by_name, nr_allocate * sizeof(new1));
+			if (!maps_by_name) {
+				/*
+				 * If by name fails, just disable by name and it will
+				 * recompute next time it is required.
+				 */
+				__maps__free_maps_by_name(maps);
+			}
+			maps__set_maps_by_name(maps, maps_by_name);
+		}
+		RC_CHK_ACCESS(maps)->nr_maps_allocated = nr_allocate;
+	}
+	memmove(&maps_by_address[first_after_index+to_add],
+		&maps_by_address[first_after_index],
+		(nr_maps - first_after_index) * sizeof(new1));
+	maps_by_address[first_after_index] = map__get(new1);
+	if (maps_by_name)
+		maps_by_name[nr_maps] = map__get(new1);
+	if (new2) {
+		maps_by_address[first_after_index + 1] = map__get(new2);
+		if (maps_by_name)
+			maps_by_name[nr_maps + 1] = map__get(new2);
+	}
+	RC_CHK_ACCESS(maps)->nr_maps = nr_maps + to_add;
+	maps__set_maps_by_name_sorted(maps, false);
+	check_invariants(maps);
+	return 0;
+}
+
 /*
  * Adds new to maps, if new overlaps existing entries then the existing maps are
  * adjusted or removed so that new fits without overlapping any entries.
@@ -743,6 +797,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
 {
 	int err = 0;
 	FILE *fp = debug_file();
+	unsigned int i;
 
 	if (!maps__maps_by_address_sorted(maps))
 		__maps__sort_by_address(maps);
@@ -751,7 +806,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
 	 * Iterate through entries where the end of the existing entry is
 	 * greater-than the new map's start.
 	 */
-	for (unsigned int i = first_ending_after(maps, new); i < maps__nr_maps(maps); ) {
+	for (i = first_ending_after(maps, new); i < maps__nr_maps(maps); ) {
 		struct map **maps_by_address = maps__maps_by_address(maps);
 		struct map *pos = maps_by_address[i];
 		struct map *before = NULL, *after = NULL;
@@ -824,9 +879,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
 				 * 'pos' mapping and therefore there are no
 				 * later mappings.
 				 */
-				err = __maps__insert(maps, new);
-				if (!err)
-					err = __maps__insert(maps, after);
+				err = __maps__insert_sorted(maps, i, new, after);
 				map__put(after);
 				check_invariants(maps);
 				return err;
@@ -839,7 +892,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
 			 */
 			map__put(maps_by_address[i]);
 			maps_by_address[i] = map__get(new);
-			err = __maps__insert(maps, after);
+			err = __maps__insert_sorted(maps, i + 1, after, NULL);
 			map__put(after);
 			check_invariants(maps);
 			return err;
@@ -869,7 +922,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
 		}
 	}
 	/* Add the map. */
-	err = __maps__insert(maps, new);
+	err = __maps__insert_sorted(maps, i, new, NULL);
 out_err:
 	return err;
 }