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Understanding Factors That Influence Performance of a Web Server. Presentation CS535 Project By Thiru. Goals. Understand how a typical web server works Infer potential factors that can influence the performance Discover the dynamics of the interactions Look at each factor in detail

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understanding factors that influence performance of a web server

Understanding Factors That Influence Performance of a Web Server

Presentation CS535 Project

By

Thiru

goals
Goals
  • Understand how a typical web server works
  • Infer potential factors that can influence the performance
  • Discover the dynamics of the interactions
  • Look at each factor in detail
  • Some miscellaneous topics, if time permits
  • Conclude
what is a web server
What Is a Web Server ?
  • A server program implementing HTTP protocol
  • A typical server would:
  • Listen on a known port (usually 80)
  • When a request arrives, create a new socket, hand it over to a helper process
  • Go back to the listening mode
  • The helper process would communicate with the client and serve the request
what is a client
What Is a Client ?
  • Typical client – a browser.
  • The steps involved in retrieving www.wpi.edu.
what are the potential bottlenecks
What Are the Potential Bottlenecks ?
  • The listening process
  • The forking model
  • The disk I/O
  • The network, i.E. The sending end
  • The scheduling model for tasks
protocol enhancement
Protocol Enhancement
  • From HTTP 1.0 to HTTP1.1
  • Persistent connections
forking
Forking
  • Spawn a new process for every request
  • Spawn a new thread for every request
  • Use events to handle requests
  • Use I/O completion mechanisms to handle processing of events
  • Use asynchronous model of execution
disk i o
Disk I/O
  • Not a pressing issue
  • A lot of small files are cached in typical server implementation
  • mmap() maps files directly to memory
enhance network i o functions
Enhance Network I/O Functions
  • Enhancements to poll()
  • Enhancements to select()
  • Declare_interest()
  • /Dev/poll on Solaris – add, modify, and remove interest sets
use asynchronous model
Use asynchronous model
  • RT signals in Linux – Abeshk Chandra’s paper.
radically new approaches
Radically new approaches
  • DB approach
  • TCP server
the big picture
The Big Picture
  • The end user experience can be enhanced in three ways
  • Replication of content – mirroring
  • Distributed caching
  • Improve WS performance
the difference between the lab and the real world
The Difference Between the Lab and the Real World
  • Slow and Indeterministic behavior of connections
  • Request sizes vary through a large range
  • In real world there are layers of caches and mirrors
the difference between the lab and the real world17
The Difference Between the Lab and the Real World
  • Network speed – connection speed – varies widely
  • It’s hard to simulate real world environment in labs. Hence the results are hard to verify
  • The test beds are not accurate – the model is skewed. S-client paper
conclusion
Conclusion
  • Factors influencing performance
  • Network I/O operations
  • Socket behavior
  • Scheduling
  • TCP implementation
  • Disk I/O does not have a big impact since small files are cached
  • A lot more, but this is what is presentable within 1800 seconds !