This is VMware physical memory management driver which acts
like a "balloon" that can be inflated to reclaim physical pages
by reserving them in the guest and invalidating them in the
monitor, freeing up the underlying machine pages so they can
be allocated to other guests. The balloon can also be deflated
to allow the guest to use more physical memory.

If unsure, say N.

To compile this driver as a module, choose M here: the
module will be called vmw_balloon.

source code:

drivers/misc//vmw_balloon.c