LXI Timing Model for Measurements

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• LXI Timing Model for Measurements
• Lynn Wheelwright

25 January 2006
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Contents

• Two timing models that represent the extreme ends
  of timing (reality is somewhere in between). Each
  block has measurable duration.
• Smart Instrument Smart Driver
• Dumb Instrument Dumb Driver
• LAN Measurement Recommendations
• Some Useful Timing Buckets (or Categories)

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Use Case Smart Instrument Smart Driver
LXI Device Physical IO Controller
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Use Case Dumb Instrument Dumb Driver
Repeat until Done
Repeat until Done
TPS Read Data
Driver format buffer cmd
OS Initiate IO transaction
Physical IO transmission
OS Receive IO transaction
Parse Execute cmds
Wait for HW to settle trigger
Measurement Acquisition
Repeat until Done
Driver Query Data
OS Initiate IO transaction
Physical IO transmission
OS Receive IO transaction
Parse Execute cmd
Format buffer data
OS Initiate IO transaction
Physical IO transmission
OS Receive IO transaction
Parse Data Format
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LAN Measurement Recommendations

• Measure Elapsed Time from entry to the driver
  until the data is returned by the driver for the
  TPS Read Data action.
• The number of Physical IO transactions should be
  measured.
• Count the number of times each Repeat until
  Done loop is executed.
• All blocks in the diagram should be measured (if
  possible)

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Useful Timing Buckets

• Controller time
• Kernel process time
• User process time
• Physical IO time
• Device time
• Kernel process time
• User process time
• Formatting time, parsing time
• Hardware settling time
• Acquisition time