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A Parameter Extraction Tool for Windows I/O
System Characterization
MASCOTS 2004
Jalil BOUKHOBZA

• The Problem Statement
• I/Os are critical.
• Windows OS Vaguely documented
• Sources are not available
• Poorly studied in academic
  research
• Hardware manufacturers documentation not
  sufficient for completely
• understanding a given I/O system and simulating
  it.
• The Objectives
• Understanding I/O flow and Performance in
  Windows systems.
• Making possible accurate simulations of the
  Windows I/O subsystem
• From the application -gt Disk mechanical
  movements

• Contributions

• Windows I/O performance measurement tool
  Measure I/O performance of a given architecture
  on a Windows OS (2000, XP, 2003)
• Empirical I/O parameters extraction tool
• Get the parameters defining the I/O subsystem to
• Understand the resultant performance
• Build accurate simulations

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• Windows I/O Performance Measurements
• Windows file access modes (Win32 CreateFile())
• Normal, sequential, random, no buffer, write
  through
• Request sizes
• Sequential / Random (accesses)
• Results
• I/O throughput
• Response times

Example of execution Configuration
Read transfer rates and response times
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• Example

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Using flags of the CreateFile() function

• Disk cache updating algorithms
• Generally simple algorithms (LRU, FIFO, LFU,
  etc.) that can be tested once the segment size
  known by issuing different read block sequences
  and then re-read the blocks to see which one is
  accessed from the disk (and so has been ejected
  from the cache).

Per request response time
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• Conclusions
• A Windows dedicated I/O performance measurement
  tool taking into account the
• different access modes (using different
  prefetching algorithms for read / write
  operations).
• Very easy to use tool to get I/O parameters. The
  extracted parameters allow to run
• accurate simulations less then 4 variation
  compared to real measures for response
• times and throughputs.

• Under development
• Allowing asynchronous file accesses
• Injecting inter arrival times
• More control on request sequentiality
• Testing more architectures
• References
• Some Studies on Windows I/Os
• 1 E.Riedel, C.VanIngen, J.Gray A performance
  study of sequential I/O on WindowsNT4, 2nd
  USENIX WindowsNT Symposium, Seattle,
• WA, 1998.
• 2 L.Chung, J.Gray, B.Worthington, R.Horst,
  Windows2000 disk I/O performance, Technical
  report MS-TR-2000-55, Microsoft Research, 2000.
• 3 J. Boukhobza, C. Timsit, On Windows File
  Access modes a Performance Study, to appear in
  the proceeding of WISICT2005,
• Cape Town, South Africa, January 2005.
• About Windows internals
• 4 D.A.Solomon, M.E.Russinovich, Inside
  Windows2000, Redmond, Washington, Microsoft
  Press, 2000.
• Caching policies
• 5 N.C Burnett, J. Bent, A.C. Arpaci-Dusseau,
  R.H. Arpaci-Dusseau, Exploiting Gray-Box
  knowledge of Buffer-cache management,

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PRiSM Laboratory, Versailles Saint Quentin
University 45 Etats Unis Avenue 78 035
Versailles Cedex E-mail  jalil.boukhobza_at_prism.uv
sq.fr