Performance Issues in WWW Servers

1
Performance Issues in WWW Servers
Erich Nahum, Tsipora Barzilai, and Dilip
Kandlur ACM SIGMETRICS Conference on Measurement
and Modeling of Computer Systems, May, 1999

• 2001. 12. 4
• Suh, Young-Ho

2
Introduction

• Goal
• Improve support for high-performance WWW servers
• Solution approach
• Optimize the operating system and the network
  protocol stack
• New socket functions
• acceptex(),transmitfile() / send_file()
• Do they provide any performance benefit?
• Does transmitfile/send_file() show any
  improvement over the already available mmap() and
  writev() system calls?
• Per-byte optimizations
• How well can we approximate a zero-copy
  integrated I/O architecture, while continuing to
  exploit the benefits of existing file systems?
• What sort of performance impact will eliminating
  data touching operations have for WWW servers?
• Per-connection optimization
• How can the per-connection overhead be reduced,
  without violating the TCP protocol sepecification?

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Background and Related Work(1/2)

• Optimize the frequency or cost of the blow
  operations

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Background and Related Work(2/2)

• Optimize OS performance directly
• Kaashoek et al.
• Customized OS (HTTP server OS)
• Druschel, Pai, and Zwaenopol
• Extensible micro-kernel OS
• Integrated I/O system for UNIX called I/O Lite
• This paper
• Like Druschel, Pai, and Zwaenopol, they believe a
  general-purpose OS is necessary to support a wide
  variety of services over HTTP, such as dynamic
  content
• However, they try to minimize changes of the API

5
Experimental Setup and Testbed(1/2)

• Hardware
• 4 IBM 43P RS/6000
• 128MB RAM, 200MHz PowerPC 604e processor
• On-chip instruction and data caches, 32KB 4-way
  associativity
• 1MB direct-mapped secondary cache
• Workload Generator
• WebStone
• Microbenchmark load the server with many
  concurrent requests for the same file
• SURGE
• Macrobenchmark load the server with concurrent
  requests for a range of files

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Experimental Setup and Testbed(2/2)

• Operating System
• AIX version 4.3.1
• With the addition of several modifications(increme
  ntal)
• acceptex(), send_file(), modified TCP protocol
  implementation
• WWW Server
• The fastest WWW Server Flash-Poll (incremental
  modification)

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Results(1/7)

• Evaluating the Proposed Socket Functions

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Results(2/7)

• Evaluating Per-Byte Optimization

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Results(3/7)

• Evaluating Per-Connection Optimizations

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Results(4/7)

• Evaluating Per-Connection Optimizations

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Results(5/7)

• Evaluating Per-Connection Optimizations

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Results(6/7)

• Evaluating Per-Connection Optimizations

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Results(7/7)

• Evaluating Overall Performance with SURGE

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Conclusion

• New socket functions
• Per-byte optimizations
• Per-connection optimizations
• Aggregate benefits