min_filelist_kbytes is incorrectly treated as a constant, but we change it dynamically when starting/stopping ARC++ and this may have an impact on the memory manager behavior under pressure.

We see some of the effects indirectly because "available" will change suddenly.  It may be good to detect changes.  We probably don't want to poll because of the cost.  Possibly memd can be notified via another D-Bus signal.