core: store unit aliases in a separate set

We allocated the names set for each unit, but in the majority of cases, we'd
put only one name in the set:

$ systemctl show --value -p Names '*'|grep .|grep -v ' '|wc -l
564
$ systemctl show --value -p Names '*'|grep .|grep ' '|wc -l
16

So let's add a separate .id field, and only store aliases in the set, and only
create the set if there's at least one alias. This requires a bit of gymnastics
in the code, but I think this optimization is worth the trouble, because we
save one object for many loaded units.

In particular set_complete_move() wasn't very useful because the target
unit would always have at least one name defined, i.e. the optimization to
move the whole set over would never fire.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/core/load-dropin.h b/src/core/load-dropin.h
index ea15554d88..5e2ec0d80a 100644
--- a/src/core/load-dropin.h
+++ b/src/core/load-dropin.h
@@ -13,7 +13,7 @@ static inline int unit_find_dropin_paths(Unit *u, char ***paths) {
                                            u->manager->lookup_paths.search_path,
                                            u->manager->unit_path_cache,
                                            ".d", ".conf",
-                                           u->names,
+                                           u->id, u->aliases,
                                            paths);
 }