1. Embedded System Lab. 김해천 haecheon100@gmail.com Decoupling Cores, Kernels, and Operating Systems Gerd Zellweger, Simon Gerber, Kornilios Kourtis, and Timothy Roscoe, ETH Zürich https://www.usenix.org/conference/osdi14/technical-sessions/presentation/zellweger

2. 김 해 천김 해 천 Embedded System Lab. Outline Motivation  Trends in hardware and software Design  Decoupling the kernel state  Booting and shutting down cores dynamically Evaluation  Kernel updates, specialized kernels

3. 김 해 천김 해 천 Embedded System Lab. What’s happening to hardware Core counts are increasing  Dark silicon  Constrained by power consumption Reconfigurable cores (dynamically changed behavior)  DVFS, Turbo Boost  Core fusion Heterogeneous cores  Fast and power hungry vs. slow and power efficient  Asymmetric multiprocessing

4. 김 해 천김 해 천 Embedded System Lab. What’s happening to software Modifying, upgrading, patching, or replacing OS kernels at runtime  K42 – dynamic kernel update  Ksplice – binary patching of linux kernels without reboot  Dtrace – modify the kernel at run time CPU Hotplug Multikernels

5. 김 해 천김 해 천 Embedded System Lab. Barrelfish/DC Design Booting a new core  boot driver manages a “target core” and encapsulates the hardware functionality to boot, suspend, resume, and power-down  boot driver abstraction treats CPU cores much like peripheral devices  only involves two processes: the boot driver, the kernel on the target core No global lock or other synchronization Home core Boot driver kernel cpu kernel

6. 김 해 천김 해 천 Embedded System Lab. Barrelfish/DC Design Shutting down a core  Highly scalable, only two cores involved cpu kernel cpu kernel OSNode Application

7. 김 해 천김 해 천 Embedded System Lab. Barrelfish/DC Design Shutting down a core  Highly scalable, only two cores involved cpu kernel OSNode O.N Application O.N Parking OSNode scheduler

8. 김 해 천김 해 천 Embedded System Lab. Barrelfish/DC Design Decoupling Cores, Kernels and Operating Systems cpu kernel OSNode cpu kernel OSNode

9. 김 해 천김 해 천 Embedded System Lab. Barrelfish/DC Design Decoupling Cores, Kernels and Operating Systems cpu kernel cpu kernel OSNode kernel

10. 김 해 천김 해 천 Embedded System Lab. Evaluation Performance of core management operation  Adding and removing cores in the system

11. 김 해 천김 해 천 Embedded System Lab. Evaluation PostgreSQL & TPC-H  Kernel Updates Shut-down target core Reboot core with a new kernel image Dispatch previous OSNode

12. 김 해 천김 해 천 Embedded System Lab. Evaluation Specialized kernels  Shut-down target core  Temporarily park the target OSNode  Boot simple real-time kernel that runs Just one application Dose not take interrupts No timers No scheduler  Temporarily provides task with hard real time gurantees

13. 김 해 천김 해 천 Embedded System Lab. http://www.barrelfish.org/zellweger-decoupling-cores.pdf https://www.usenix.org/conference/osdi14/technical- sessions/presentation/zellweger