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Lecture 7: Performance Issues with Virtualization

Lecture 7: Performance Issues with Virtualization. Xiaowei Yang (Duke University). Recap . What’s cloud computing Security issues. Today. How v irtualization impacts performance (measurement) The Impact of Virtualization on Network Performance of Amazon EC2 Data Center

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Lecture 7: Performance Issues with Virtualization

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  1. Lecture 7: Performance Issues with Virtualization Xiaowei Yang (Duke University)

  2. Recap • What’s cloud computing • Security issues

  3. Today • How virtualization impacts performance (measurement) • The Impact of Virtualization on Network Performance of Amazon EC2 Data Center • Guohui Wang, T. S. Eugene Ng • Performance Profiling in a Virtualized Environment • JiaqingDu, NipunSehrawat, and Willy Zwaenepoel

  4. Virtualization Impacts Network Performance • Cloud computing uses virtualization to provide resource sharing • Time sharing • Processors, NIC, harddisk, performance monitoring unit Guest0 Guest1 Dom0 Driver domain Xen NIC

  5. Measure the impact of virtualization • Processor sharing • Packet round-trip delay • TCP/UDP throughput • Packet loss

  6. Processor sharing • Measurement methodology • CPUTest: loops for a million times • Gettimeofday() at the beginning and end of the loop • Saves timestamps in memory • Dump the saves timestamps to disks

  7. Packet round-trip delay • 10 ping probes per second, 5000 round-trip delay measurements

  8. TCP/UDP throughput • UDPTest • The program itself must be able to read and send data as fast as possible 128KB UDPSend UDPRecv Dom0 Dom0 Xen Xen NIC NIC

  9. TCP/UDP throughput 128KB • TCPTest • Send and Receive window set to 256KB • 0.5ms •  4Gbps TCPSend TCPRecv Dom0 Dom0 Xen Xen NIC NIC

  10. Packet loss • Badabing • Packet loss estimation • Active probes and statistical estimations

  11. Experiments setup: spatial • Across different instances, availability zone • For each availability zone (3 total) • 250 pairs of small instance • 50 pairs of medium instances • TCP/UDP • May congest the network • Limit to 800MB data • Badabing • One minute

  12. Experiments setup: temporal • Over a period of time • Two small instance pairs and one medium in each of the availability zone • Processor sharing, network performance, and packet loss • Round by round for 150 hours • Each round separate for 10 minutes

  13. Results

  14. Processor sharing

  15. How to compute CPU share • Loop > 1ms  off • Loop ~ 3us  on

  16. Distribution of CPU share

  17. Bandwidth measurement results

  18. Bandwidth measurement results

  19. A closer look

  20. Medium instances’ performance

  21. Why? • TCP/UDP sender is scheduled off • UDP > TCP • Sender can send when receiver is scheduled off

  22. End-to-end delays

  23. Why • Queuing? • Unlikely, rare packet loss • <500Mb/s TCP throughput  no congestion • Receiver scheduled off •  no reply until it’s on again

  24. Packet loss estimation

  25. Why? • Measurement tool not considering virtualization does not fit • Badabing detects loss episodes • Loss episode • A packet loss within some time of now • One way delay is larger than a threshold •  Large variation leads to a high loss estimate

  26. Badabing overestimates loss

  27. Implications • Delay = queuing + transmission + propagation + scheduled off • Affect the fidelity of network testing if using small instances • May cause performance problems for some applications •  yet to be validated

  28. Discussion • Easy fix: using medium or large instances • I/O sharing • Better way to share networks? • Ways to detect whether you are sharing with another instance • Try it on other instances?

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