1. A machine-implemented method for sharing programmatic modules among isolated virtual machines, the method comprising: copying, from a shareable memory region that is readable by multiple isolated virtual machines, into a first private memory region of a first virtual machine, first data that a second virtual machine (a) loaded from a programmatic module, (b) stored into a second private memory region of the second virtual machine, and (c) copied, from the second private memory region, into the shareable memory region; and establishing a mapping between the first virtual machine and a particular area of the shareable memory region that contains second data that the second virtual machine (a) loaded from the programmatic module and (b) stored into the particular area of the shareable memory region; wherein the mapping enables the first virtual machine to read the second data without creating a copy of the second data in any private memory region of the first virtual machine; and wherein the first private memory region and the second private memory region both begin at a same virtual address.