Reinder J. Bril, [e-mail]

1
Exercise

• Relation between virtual time and real time
• DescriptionConsider two situations for two RCEs
  R1 and R2 running on a single physical platform,
  where the budgets of the RCEs have periods T1
  50 and T2 70, respectively. These budget
  periods correspond with the periods of the RCEs.
• (a)    The RCEs receive budgets B1 20 and B2
  30, respectively, which correspond with their
  computation times.
• (b)   The RCEs receive budgets B1 20 and B2
  42, respectively, corresponding with their
  computation times.
• Questions
• Determine the schedulability of the budgets for
  the situations (a) and (b) under both FPPS (i.e.
  RMS) and EDF.
• Determine the lateness for R2 under RMS for B2
  42.
• How many additional buffers would be required to
  allow the output of R2 to be shown without jitter
  under RMS ? Note that the absolute deadline of
  the output has been decoupled from processing by
  means of those additional buffers.

2
Exercise (continued)

• Questions (continued)
• Let the budget scheduler only provide budgets
  under RMS at a period of 50 (i.e. the budget of
  R1 receives a higher priority than the budget of
  R2, but the periods at which the budgets are
  provided are equal to 50) .
• How much budget would have to be provided to R2
  for situation (b) ?
• How could the virtual time be determined
  (allowing R2 to adapt to get by with its
  budget), assuming that budgets are always
  completely consumed (independent of who actually
  consumes the budget) ?