CPU scaling benchmark

W=0 W=1 W=2 W=3 W=4 W=6 W=8 W=9 W=10 W=12 W=16 iters: 100M 500M 1B 2B
workers
6 +1 main
iters total
500M
71428571/stream
elapsed
1196.93 ms
total CPU used
7313.38 ms
speedup
6.11×
vs serial
efficiency
87.3%
of 7× ideal
stream spawn ms spawned@ work start@ work end@ work ms reap wait ms
0 (main) 0 10.01 10.02 1166.45 1156.43 0
1 1.906 1.92 25.68 1035.33 1009.65 0.15
2 1.483 3.43 17.49 856.23 838.74 0.21
3 1.464 4.91 41.65 1194.16 1152.51 27.83
4 2.045 6.98 32.6 1105.42 1072.82 0.22
5 1.493 8.49 43.03 1144.06 1101.03 0.25
6 1.482 9.99 26.56 1008.76 982.2 0.27
main
w1
w2
w3
w4
w5
w6
    fork+handshake      CPU work      parent reap wait
what this measures
Each stream runs a tight integer LCG loop — working set is one CPU register, no memory access, no shared data. Speedup = sum(stream CPU time) / wall-clock elapsed. Efficiency = speedup / (workers+1). 100% efficiency means perfect linear scaling; less than 100% is the cost of serial fork setup, reap tail, SMT/core contention.