Enhancements to daily-sweeper routine to reduce CPU load (#8209)

- ListObjectsHeal should list only objects
  which need healing, not the entire namespace.
- DeleteObjects() to be used to delete 1000s of
  objects in bulk instead of serially.

cmd/daily-lifecycle-ops.go

@@ -139,22 +139,24 @@ func lifecycleRound(ctx context.Context, objAPI ObjectLayer) error {
 			if err != nil {
 				continue
 			}
+			var objects []string
 			for _, obj := range res.Objects {
 				// Find the action that need to be executed
 				action := l.ComputeAction(obj.Name, obj.ModTime)
 				switch action {
 				case lifecycle.DeleteAction:
-					objAPI.DeleteObject(ctx, bucket.Name, obj.Name)
+					objects = append(objects, obj.Name)
 				default:
-					// Nothing
-
+					// Do nothing, for now.
 				}
 			}
+			// Deletes a list of objects.
+			objAPI.DeleteObjects(ctx, bucket.Name, objects)
 			if !res.IsTruncated {
+				// We are done here, proceed to next bucket.
 				break
-			} else {
-				marker = res.NextMarker
 			}
+			marker = res.NextMarker
 		}
 	}