Uploaded byHawx Chen
[TALK] Exokernel vs. Microkernel
The document outlines the principles of exokernels and compares them to traditional microkernel and monolithic kernel architectures. It emphasizes the historical context of operating systems, explaining concepts like page handling and user-mode execution. The author, a senior software engineer, shares insights on implementing operating systems and the importance of co-design between applications and OS for enhanced scalability.
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[TALK] Exokernel vs. Microkernel
- 1. 陳膺正 (Hawx Chen) yingjheng.chen@gmail.com http://hawxchen.blogspot.tw Exokernel vs. Microkernel
- 2. Who Am I •Experience – 2008 NCTU CS Bachelor – 2010 NTU CSIE Master – 2010~presnet MStar Semiconductor • Senior software engineer • Talk: – 2012 COSCUP. – 2013 COSCUP. • Open Source – https://github.com/HawxChen/MIT-6.828-Adventure Enjoy to implement OS.
- 3. Outline • Importance ofHistory • Base Arch • Exokernel Principle • Example: page handling • Geek Part
- 4. Outline • Importance ofHistory • Base Arch • Exokernel Principle • Example: page handling • Geek Part
- 5. Importance of History UnicsUNIXv6 MINIXMTS LinuxBSD L4 1975 Exokernel 199519871967 1969 1978 1991 Time
- 6. Importance of history A.D1967 Hardware
- 7. Importance of history Hardware Exokernel LibOS App LibOS’ App’ LibOS’’ App’’ PagerSwapper Ignore pag e fault A.D 1995 User mode Kernel mode
- 8. Outline • Importance ofHistory • Base Arch • Exokernel Principle • Example: page handling • Geek Part
- 9. UNIX Arch User Process SystemCall Interface (Library Routines) User Process Hardware Process Management Memory Management File System I/O Services Scheduler I/O Buffers Device Drivers Kernel Space
- 10. MINIX Arch Kernel Space Scheduler/message passing Memory copy
- 11. Exokernel Arch: Aegis/ExOS KernelSpace Libs’Libs ExOS has TCP, IPC, and FS. App App’ ExOS’ has VM, POSIX, and Scheduler. Libs’’ ExOS’’ has Timer Service Routine. App’’ Disk TLB Network Memory Frame buffer Resource Allocation Resource Revocation Information Query Protection
- 12. Outline • Importance ofHistory • Base Arch • Exokernel Principle and Design • Example: page handling • Geek Part
- 13. Exokernel Principle 1. Separateprotection from management 2. Expose Names 3. Expose allocation 4. Expose Revocation 5. Expose Information
- 14. Library Operating System (Replaceable) Exokernel Approach VMIPC Traps Vecs Distributed Shared MemoryWWW POSIX TCP Disk TLB Network Memory Frame buffer Mosaic Barnes-HutApps Library Kernel HW Expose allocation/revocation/names/information, and Support Protection
- 15. Exokernel Approach VMIPC Traps Vecs Distributed Shared Memory WWW POSIXTCP Expose allocation/revocation/names/information, and Support Protection Disk TLB Network Memory Frame buffer Mosaic Barnes-Hut CPL = 3 CPL = 0 Library Operating System (Replaceable ) Apps Library Kernel HW
- 16. Design: Monolithic kernel Hardware Scheduler TimerServices IPC, Signal, System Calls, POSIX File Systems: ext2, ext3, NFS,… etc. VFS Memory manager. … … Device drivers Proc1 Proc2 Proc3 Proc4 Proc5 Proc6 Proc7 Kernel Space
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- 18. Design: Exokernel WWW POSIX TCP Exposeallocation/revocation/names/information, and Support Protection Mosaic VMIPC Traps Distributed Shared Memory Barnes-Hut Kernel Space Hardware
- 19. Outline • Importance ofHistory • Base Arch • Exokernel Principle • Example: page handling • Geek Part
- 20. Exokernel Way Page fault Exception PageFault Handler LibOS App Pager LibOS App Pager: Now You See Me.( Exception Vector Table Hardware Exokernel …………. …………. …………. …………. …………. 1. Trigger the page fault exception 2. Query exception vector table 3. Page fault handler (trick) 4. Translate to real pager 5. Allocate a free page 6. Map 7. UnMap 8. Adjust the stack (trick) 9. Return to the fault happening instruction CPL = 3 CPL = 0
- 21. Outline • Importance ofHistory • Base Arch • Exokernel Principle • Example: page handling • Geek Part
- 22. Geek Part • Makepage fault handler execute in user mode. – Expose something out of kernel – The stack trick • Implementation: – https://github.com/HawxChen/MIT-6.828- Adventure/tree/lab4
- 23. Stack Page Fault Happening. WWW POSIX TCP Exposeallocation/revocation/names/information, and Support Protection Disk TLB Network Memory Frame buffer Mosaic Apps Library Operating System (Replaceable ) Exokernel HW CPL=3 CPL=0User Context Pager 0xEEEEEEEE: esp 0xBBBBBBBB:esp 0x00001688:eip &(pager):eip EIP: 0x00001688 -> &(pager):eip ESP: 0xEEEEEEEE -> 0xBBBBBBBB Page fault handler Page fault handler (trick) Adjust the stack (trick) 0x00001688:eip ret
- 24. Conclusion • App andOS co-design. • Application driven design. • Don’t limit app’s scalability. – Everyone is ambitious.
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