perf maps: Reduce sorting for overlapping mappings

When an 'after' map is generated the 'new' map must be before it so
terminate iterating and don't resort. If the entry 'pos' is entirely
overlapped by the 'new' mapping then don't remove and insert the
mapping, just replace - again to remove sorting.

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

Before:
real    0m9.856s
user    0m9.637s
sys     0m0.204s

After:
real    0m5.894s
user    0m5.650s
sys     0m0.231s
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/20240521165109.708593-3-irogers@google.com

tools/perf/util/maps.c

@@ -744,7 +744,6 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
 	int err = 0;
 	FILE *fp = debug_file();
 
-sort_again:
 	if (!maps__maps_by_address_sorted(maps))
 		__maps__sort_by_address(maps);
 
@@ -820,36 +819,54 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
 			/* Maps are still ordered, go to next one. */
 			i++;
 			if (after) {
-				err = __maps__insert(maps, after);
-				map__put(after);
-				if (err)
-					goto out_err;
-				if (!maps__maps_by_address_sorted(maps)) {
-					/*
-					 * Sorting broken so invariants don't
-					 * hold, sort and go again.
-					 */
-					goto sort_again;
-				}
 				/*
-				 * Maps are still ordered, skip after and go to
-				 * next one (terminate loop).
+				 * 'before' and 'after' mean 'new' split the
+				 * 'pos' mapping and therefore there are no
+				 * later mappings.
 				 */
-				i++;
+				err = __maps__insert(maps, new);
+				if (!err)
+					err = __maps__insert(maps, after);
+				map__put(after);
+				check_invariants(maps);
+				return err;
 			}
+			check_invariants(maps);
 		} else if (after) {
+			/*
+			 * 'after' means 'new' split 'pos' and there are no
+			 * later mappings.
+			 */
 			map__put(maps_by_address[i]);
-			maps_by_address[i] = after;
-			/* Maps are ordered, go to next one. */
-			i++;
+			maps_by_address[i] = map__get(new);
+			err = __maps__insert(maps, after);
+			map__put(after);
+			check_invariants(maps);
+			return err;
 		} else {
+			struct map *next = NULL;
+
+			if (i + 1 < maps__nr_maps(maps))
+				next = maps_by_address[i + 1];
+
+			if (!next  || map__start(next) >= map__end(new)) {
+				/*
+				 * Replace existing mapping and end knowing
+				 * there aren't later overlapping or any
+				 * mappings.
+				 */
+				map__put(maps_by_address[i]);
+				maps_by_address[i] = map__get(new);
+				check_invariants(maps);
+				return err;
+			}
 			__maps__remove(maps, pos);
+			check_invariants(maps);
 			/*
 			 * Maps are ordered but no need to increase `i` as the
 			 * later maps were moved down.
 			 */
 		}
-		check_invariants(maps);
 	}
 	/* Add the map. */
 	err = __maps__insert(maps, new);