RTWG-discussion-points

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Review of test programs

lpptest

problems:

  • requires 2 machines
  • requires parallel port (not many embedded boards have this)
  • uses TSC, which is i386-specific

benefits:

  • built into the rt-preempt patch
  • 2-machine system gives unbiased timing results
    • instrumentation does not interfere with the timings

realfeel

benefits:

  • is one-machine
  • uses /dev/rtc, does not use timer interrupt
    • this isolates the ISR handling from timer operations
  • is a very simple test

problems:

  • uses TSC, which is i386-specific
  • doesn't have an instrumentation point in the kernel
    • no measurement of int latency, only process start latency
  • process start latency is "guessed" from expected interrupt time
    • that is, it is not actually measured
  • not all boards have a working /dev/rtc driver


igel test

This tests scheduling latency on receipt of a character on an SM501 uart. The UART driver gets a timestamp on ISR start, and can be asked for them from user-space after a run. The user-space driver measures the time from ISR start to task start. Test is specific to SH architecture. Uses SH hardware timer.

See http://tree.celinuxforum.org/CelfPubWiki/UserLevelDeviceDriver (page is in Japanese)

  • Yung Joon will ask Takao Ikoma to translate this page.
  • Matsubara-san will update the driver and some of the text on the page.
    • will attach latest driver source
  • Tim will provide Ikoma-san e-mail