L4

Memory Allocation
Hands all memory to a server known as sigma0
Sigma0 gives out memory to anyone who asks and marks it as allocated
Typically, the user-space VMM requests all of the memory at boot time

Low Level Management
Provides a map and unmap interface
Real VMM is built on top

Paging Policy
Chosen and enforced by the user-space VMM

Paging
Each thread in L4 has a (user chosen) pager thread
When a page fault occurs, the kernel sends an RPC to the thread's pager
Pager must find the page and install it