1. Jennifer Rose Daniel Stanaland Amy Turlington
Exokernel
Jennifer Rose
Daniel Stanaland
Amy Turlington

2. Overview Exokernel: thinnest possible kernel
Multiplexes, does not abstract
Primitive interface most utilizable
Most of functionality in application space
Similar to microkernel

3. Application/User Space
Exokernel Model
Application/User Space
Applications
Library OS: ExOS
Exokernel: Xok, Aegis
Hardware

4. Resource Management Kernel multiplexes resources
Resources managed through application layer
Kernel enforces protections
Permissions
Mutex
Etc.

5. Privileged Instructions & Deadlock
Delegate management to applications
Applications have access to privileged instructions
Detection and Resolution (for multiprocessing)
message queue

6. Data Structures Process Management Numeric id of a process’s parent
Running status
Program name
Quantum

7. Data Structures Memory Management File Management
Disk arm positions, cached TLB
Approximate least-recently-used ordering of all physical pages
File Management
Reuses the applications data structures
Reduces redundant bookkeeping

8. Process Model Process = environment Capabilities Entry points
Page table
Accounting information
U-area

9. Scheduling Fixed time quantum per process
Context-switching by applications
Prologue and epilogue code
“Sleeping” processes
Wakeup predicates

10. Protected Sharing Strong critical sections for mutual exclusion
Disabled software interrupts
Software regions
Capabilities (permissions)
Wakeup predicates

11. Fin