ActorCache was introduced in MW 1.37 after an evolution of T273974. There should be parameters to control this cache, similarly to other caches in MediaWiki, or at least a parameter to disable this cache.

I spent a few hours to track errors in Semantic MediaWiki tests, and it was solved by disabling this cache (see #5320), probably because it introduces incoherences between the state of the database and of this in-memory cache at the beginning of some tests depending on the previous tests. (You can see also in #5319 an attempt to restart the services ActorStore and ActorStoreFactory at the beginning of each test, but it is not a very robust way to solve the issue and did not completely solved all tests, at the contrary of disabling the ActorStore cache.)

I request at least a parameter to control this cache (for example the size of this cache, including the size 0 to disable it), or possibly more parameters like with the standard $wgObjectCaches.