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Quantitative Evaluation of Embedded Systems. Latency for a delayed periodic source. Calculating a latency bound. Given a dataflow graph with execution times E a Determine the MCM and choose a period μ ≥ MCM Determine start-times T a of a periodic schedule
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Quantitative Evaluation of Embedded Systems Latency for a delayed periodic source
Calculating a latency bound • Given a dataflow graph with execution times Ea • Determine the MCM and choose a period μ ≥ MCM • Determine start-times Ta of a periodic schedule • Determine the minimum number δ of tokens between input and output • Latency ≤Toutput+ Eoutput + δ·μ
Latency for a delayed source t0 = 0ms A C B t0 = 34ms t0 = 8ms 30ms S Latency = 10ms MCM = 22ms 26ms
Latency for a delayed source t0 = 0ms A C B t0 = 34ms t0 = 8ms 30ms S D Latency = 10ms MCM = 22ms 26ms Delay = 34ms
Calculating a delayed latency bound • Given a dataflow graph with execution times Ea • Determine the MCM and choose a period μ ≥ MCM • Determine start-times Ta of a periodic schedule • Determine the minimum number δ of tokens between input and output • Delayed latency ≤Toutput+ Eoutput + δ·μ- Tinput
Latency for a delayed source A C B 30ms E 10ms 15ms 26ms
Latency for a delayed source 0ms A C B 0ms 34ms 8ms 30ms S E D 10ms 15ms Delay = MCM = 22ms 26ms
Latency for a delayed source • Determine the MCM and choose a period μ ≥ MCM • For each actor a initialize a start-time Ta := 0 • Repeat for each arc a—i—b : Tb := Tb max (Ta + Ea – iμ)until there are no more changes • Repeat for each actor a:Ta:= min{all arcs a-i-b} (Tb - Ea+ iμ)until there are no more changes • Delayed latency ≤ Toutput+ Eoutput + δ·μ - Tinput