* Check if the page selection algorithm is working well
* Divide swappability of objects by refcount
* Use multiple open FDs against the VM file, one for thread.
-* EXISTS should avoid loading the object if possible without making the code too specialized.
* vm-min-age <seconds> option
* Make sure objects loaded from the VM are specially encoded when possible.
* Check what happens performance-wise if instead to create threads again and again the same threads are reused forever. Note: this requires a way to disable this clients in the child, but waiting for empty new jobs queue can be enough.