Scale the Work
The same CPU-heavy job at four sizes. Pick an execution model at each rung before the numbers appear — because the right answer changes twice on the way up, and the first change is the one engineers reach for too early while the second is the one they reach for too late.
SIMULATED
No number on this page was measured. Wall-clock figures come from the concurrency model, given eight cores and a 40 ms task. The model reproduces the behaviour of real systems — work does not overlap on one core, a critical section serialises whatever fraction of the work it covers, a queue whose arrival rate exceeds its service rate grows without bound — but the figures belong to no real machine, runtime or workload. Read the shape of the curve and the direction of the change; never quote the milliseconds.
Rung 1
10 tasks
Tasks
10
CPU per task
40 ms
Cores
8
Sequential wall time
400 ms
Commit to an execution model
One choice, before any figure is shown.
Ten CPU-heavy tasks, each about 40 ms of pure computation. How do you run them?
Nothing below is shown until you commit. Deciding wrong and being told why is the exercise.
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