Snapshot restore

Snapshot restore starts a sandbox from the memory image of an already-booted environment instead of booting a guest and starting processes.

Snapshot restore treats memory the way that copy-on-write treats the root filesystem. Instead of booting a guest and starting processes, the sandbox runtime restores a snapshot of an already-booted environment. The runtime maps the memory image and loads pages only as they are touched. A sandbox with a ready language runtime can therefore appear in far less time than that language runtime takes to start.