Virtual Memory sub-TODO:
* Check if the page selection algorithm is working well.
-* Fix support for large files
* Divide swappability of objects by refcount
-* While loading DB from snapshot or AOF, swap objects as needed if maxmemory
- is reached, calling swapOneObject().
* vm-swap-file <filename>. The swap file should go where the user wants, and if it's already there and of the right size we can avoid to create it again.
+* it should be possible to give the vm-max-memory option in megabyte, gigabyte, ..., just using 2GB, 100MB, and so forth.
+* redis-cli vmstat, calling INFO every second and printing VM stats ala vmstat.
+* protect zmalloc memory usage increments with a mutex
VERSION 1.6 TODO (Virtual memory)
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