1. 2011/08/09 Sunwook Bae

2. Contents Paper Info Introduction Overall Architecture Resource Management Evaluation Conclusion References

3. Paper Info (1/2) Publish In Proceedings of the 13th IEEE International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems(MASCOTS), Sept. 2005 Author Le Yan, Lin Zhong, Niraj K. Jha Department of Electrical Engineering Princeton University Ph.D. Students graduated, Sept. '06

4. Paper Info (2/2) Documents Joint dynamic voltage scaling and adaptive body biasing for heterogeneous distributed real-time embedded systems (IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems 24 (7), pp. 1030-1041) User-perceived latency driven voltage scaling for interactive applications (Proceedings – ACM Design Automation Conference 2005, art. no. 38.3, pp. 624-627) Combined Dynamic Voltage Scaling and Adaptive Body Biasing for Heterogeneous Distributed Real-time Embedded Systems (IEEE/ACM International Conference on Computer-Aided Design 2003, Digest of Technical Papers, pp. 30-37)

5. Introduction (1/2) Approach Problem: existing OSs do not provide satisfactory responsiveness Propose a holistic approach Process scheduling Memory management Disk I/O scheduling Dynamic voltage scaling (DVS) X client scheduling in the X Windows system

6. Introduction (2/2) Modern interactive applications are from Textual app to Video games, sophisticated simulation, and virtual reality environments Inaccurate interactivity estimation CPU load [1] vs I/O load [2] TuxRacer [3]: CPU bounded I/O bounded CPU usage 96%

7. Overall Architecture (1/2)

8. Overall Architecture (2/2) SetXserverPid() Notify the pid of the X server to the kernel as soon as the X server is started and give a priority bonus SetFocusProcess() Reset priorities and find the processes currently under user focus, and then set their focus_flag Boost the priorities and maximizes the page ages SetCpuSpeed() Adjust the frequency/supply voltage based on the information on the user-perceived latency [7]

9. Resource Management (1/5) Tracking of Processes Under Focus Pid Window server Window client [4]

10. Resource Management (2/5) Process management Add a new field (focus_flag) to the task descriptor indicating that the process is currently under user focus 1 for leaf-focus process 2 for other processes under user focus 0 for others Once the user switches focus, the kernel clears and resets the focus-flag The priorities of the processes under user focus are boosted (gives a bonus value -15)

11. Resource Management (3/5) Memory management Reduce the page faults of the processes under user focus Maximize the age of the pages in the code segment of the leaf-focus process

12. Resource Management (4/5) Disk I/O scheduling Look [24]: keep moving in one direction and switch I/O request 89, 185, 45, 127, 56, 123, 68, 72, 23

13. Resource Management (5/5) X client scheduling X server to give the X client under user focus the highest priority temporarily [6] Latency-driven DVS [7]

14. Evaluation (1/3) IBM Thinkpad R32 laptop RedHat Linux 9.0 with 2.4.20 kernel, with XFree86 4.3 and KDE desktop environment

15. Evaluation (2/3)

16. Evaluation (3/3)

17. Conclusion Propose and implement a user focus-aware resource management technique Show how computer responsiveness can be improved in the Linux/X system Only minimal changes Fully based on existing process, memory, and disk I/O mechanisms in Linux The impact on background applications is still in the acceptable range

18. References [1] I. Molnar, “Goals, design and implementation of the new ultra-scalable O(1) scheduler,” Jan. 2002 [2] Y. Etsion, D. Tsafrir, and D. Feitelson, “Human-centered scheduling of interactive and multimedia applications on a loaded desktop,” Tech. Rep., Hebrew University, Mar. 2003. [3] TuxRacer, http://www.tuxracer.com.http://www.tuxracer.com [4] Y. Endo and M. Seltzer, “Improving interactive performance using TIPME,” in Proc. ACM Int. Conf. Measurement & Modeling of Computer Systems, 2000.

19. References [5] Linux kernel source code, version 2.4.20, http://lxr.linux.no/source/drivers/block/elevator.c. http://lxr.linux.no/source/drivers/block/elevator.c [6] K. Packard, “Efficiently scheduling X clients,” in Proc. USENIX Technical Conf., 2000 [7] L. Yan, L. Zhong, and N. K. Jha, “User-perceived latency driven voltage scaling for interactive applications,” in Proc. Design Automation Conf., 2005