1. Performance Evaluation of Load Sharing Policies on a Beowulf Cluster James Nichols Marc Lemaire Advisor: Mark Claypool

2. Outline Introduction Methodology Results Conclusions

3. Introduction What is a Beowulf cluster? Cluster of computers networked together via Ethernet Load Distribution Share load, decreasing response times and increasing overall throughput Need for expertise in a particular load distribution mechanism Load Historically use CPU as the load metric. What about disk and memory load? Or system events like interrupts and context switches? PANTS Application Node Transparency System Removes the need for expertise required by other load distribution mechanisms

4. PANTS PANTS Application Node Transparency System Developed in previous MQP: CS-DXF-9918. Enhanced the following year to use DIPC in: CS-DXF- 0021 Intercepts execve() system calls Uses /proc files system to calculate CPU load to classify node as “busy” or “free” Any workload which does not generate CPU load will not be distributed Near linear speedup for computationally intensive applications  New load metrics and polices!

5. Outline Introduction Methodology Results Conclusions

6. Methodology Identified load parameters Implemented ways to measure parameters Improved PANTS implementation Built micro benchmarks which stressed each load metric Built macro benchmark which stressed a more realistic mix of metrics Selected real world benchmark

7. Methodology: Load Metrics Acquired via /proc/stat CPU – Totals jiffies (1/100ths of a second) that the processor spent on user, nice, and system processes. Obtain a percentage of total. I/O – Blocks read/written to disk per second. Memory – Page operations per second. Example: a virtual memory page fault requiring a page to be loaded into memory from disk Interrupts – System interrupts per second. Example: incoming Ethernet packet. Context Switches – How many times the processor switched between processes per second.

8. Methodology: Micro & Macro Benchmarks Implemented micro and macro benchmarks Helped refine understanding of how the system was performing, tested our load metrics, etc. (Not enough time to present)

9. Real world benchmark: Linux kernel compile Distributed compilation of the Linux kernel Executed by the standard Linux program make Loads I/O and memory resources Details: Kernel version 2.4.18 432 files Mean source file size: 19KB Needed to expand relative path names to full paths Thresholds Pants default: CPU: 95% New policy: CPU: 95%, I/O: 1000 Blocks/sec, Memory: 4000 Page faults/sec, IRQ: 115000 interrupts/sec, Context Switches: 6000 switches/sec  Compare PANTS default policy to our new load metrics and policy

10. Outline Introduction Methodology Results Conclusions

11. Results: CPU

12. Results: Memory

13. Results: Context Switches

14. Results: Summary

15. Conclusions Achieve better throughput and more balanced load distribution when metrics include I/O, memory, interrupts, and context switches. Future Work: Use preemptive migration? Include network usage load metric. For more information visit: http://pants.wpi.edu Questions?