Memory Policy

Policy Server
Has knowledge of the Hurd interfaces
Tasks negotiate contracts for guaranteed physical pages
Total number of guaranteed pages will never exceed the number of frames
Tasks may ask for extra pages

Guaranteed Pages
Negotiated at task creation time
May be a function of uids
Medium term contracts
Renegotiated occasionally
Total number of guaranteed pages will never exceed total frames

Extra Page
Page allocation is done only when actually needed
Tasks may be given extra pages if there is no memory pressure
Extra pages must be freed on short notice
If the task fails to do this, VMM may revoke all memory