1. Exokernel: An Operating System Architecture for Application-Level Resource Management By Dawson R. Engler, M. Frans Kaashoek, James O’Toole Jr. Presented by Seth Goldstein EECS 582 – W161

2. Outline Traditional Operating System Exokernel Implmentation Kernel Comparisons Conclusion EECS 582 – W162

3. Outline Traditional Operating System Exokernel Implmentation Kernel Comparisons Conclusion EECS 582 – W163

4. Traditional Operating System Centralized resource management All applications must use the same abstractions High-level abstractions Overly general Provide all features possible Implementation cannot be modified Limited functionality Information is hidden EECS 582 – W164

5. Outline Traditional Operating System Exokernel Implmentation Kernel Comparisons Conclusion EECS 582 – W165

6. Exokernel and Library Operating Systems Implement traditional abstractions at the user-level EECS 582 – W166

7. Hypotheses Exokernels can be very efficient Low-level, secure multiplexing of hardware resources can be implemented efficiently Traditional operating system abstractions can be implemented efficiently at application level Applications can create special-purpose implementations of these abstractions EECS 582 – W167

8. Library Operating Systems Simpler Specialized Multiple can exist Few Kernel crossings EECS 582 – W168

9. Exokernel Design Avoid resource management Allow the request of specific resources Visible resource revocation Secure bindings Downloading code Abort protocol Extendable EECS 582 – W169

10. Outline Traditional Operating System Exokernel Implmentation Kernel Comparisons Conclusion EECS 582 – W1610

11. Aegis Scheduling Processor events Exceptions Protected Control Transfers EECS 582 – W1611 Time to perform null procedure and system call (µs) Exception dispatch time (µs)

12. ExOS: Interprocess Communication (IPC) EECS 582 – W1612 IPC time

13. ExOS: Virtual Memory EECS 582 – W1613 Virtual memory operations (µs)

14. ExOS: Application-Specific Safe Handlers (ASH) EECS 582 – W1614 60-byte roundtrip latency over Ethernet (µs) Roundtrip Latency vs Number of Processes

15. Outline Traditional Operating System Exokernel Implmentation Kernel Comparisons Conclusion EECS 582 – W1615

16. Kernel Comparisons EECS 582 – W1616 Exokernel Multikernel

17. Other Related Systems NanoKernel Virtual Machines EECS 582 – W1617

18. Outline Traditional Operating System Exokernel Implmentation Kernel Comparisons Conclusion EECS 582 – W1618

19. Conclusion Exokernels can be very efficient The lower the level of a primitive the more efficient it is EECS 582 – W1619

20. Questions and Discussion EECS 582 – W1620

21. References http://web.eecs.umich.edu/~mosharaf/Readings/Exokernel.pdf http://web.eecs.umich.edu/~mosharaf/Readings/Multikernel.pdf https://www.cs.utexas.edu/~dahlin/Classes/GradOS/papers/kaashoek97sosp.pdf https://thelinuxdesk.wordpress.com/tag/monolithic-kernel/ https://en.wikipedia.org/wiki/Monolithic_kernel#/media/File:OS-structure2.svg EECS 582 – W1621