* Divide swappability of objects by refcount
* 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.
-* Make sure to wait all the IO threads are done before to fork() for BGSAVE and BGREWRITEAOF
-* Enlarge the stack of threads, to problems when calling LZF lib.
* 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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