perf dsos: When adding a dso into sorted dsos maintain the sort order

dsos__add would add at the end of the dso array possibly requiring a
later find to re-sort the array. Patterns of find then add were
becoming O(n*log n) due to the sorts. Change the add routine to be
O(n) rather than O(1) but to maintain the sorted-ness of the dsos
array so that later finds don't need the O(n*log n) sort.

Fixes: 3f4ac23 ("perf dsos: Switch backing storage to array from rbtree/list")
Reported-by: Namhyung Kim <[email protected]>
Signed-off-by: Ian Rogers <[email protected]>
Cc: Steinar Gunderson <[email protected]>
Cc: Athira Rajeev <[email protected]>
Cc: Matt Fleming <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Namhyung Kim <[email protected]>

Author: captain5050

tools/perf/util/dsos.c

@@ -206,11 +206,27 @@ int __dsos__add(struct dsos *dsos, struct dso *dso)
 		dsos->dsos = temp;
 		dsos->allocated = to_allocate;
 	}
-	dsos->dsos[dsos->cnt++] = dso__get(dso);
-	if (dsos->cnt >= 2 && dsos->sorted) {
-		dsos->sorted = dsos__cmp_long_name_id_short_name(&dsos->dsos[dsos->cnt - 2],
-								 &dsos->dsos[dsos->cnt - 1])
-			<= 0;
+	if (!dsos->sorted) {
+		dsos->dsos[dsos->cnt++] = dso__get(dso);
+	} else {
+		int low = 0, high = dsos->cnt - 1;
+		int insert = dsos->cnt; /* Default to inserting at the end. */
+
+		while (low <= high) {
+			int mid = low + (high - low) / 2;
+			int cmp = dsos__cmp_long_name_id_short_name(&dsos->dsos[mid], &dso);
+
+			if (cmp < 0) {
+				low = mid + 1;
+			} else {
+				high = mid - 1;
+				insert = mid;
+			}
+		}
+		memmove(&dsos->dsos[insert + 1], &dsos->dsos[insert],
+			(dsos->cnt - insert) * sizeof(struct dso *));
+		dsos->cnt++;
+		dsos->dsos[insert] = dso__get(dso);
 	}
 	dso__set_dsos(dso, dsos);
 	return 0;