The prior _COST_MODEL/_FIXED_OVERHEAD_S were fit only against local
synthetic benchmarks (up to 2M rows/side), which can't see docker
pull or real /ceph read latency and wildly overestimated real jobs
(~1200-1800s predicted vs 50-320s median actual, from condor_history
on production run 563f5ee3, --chunks 4, ~254M total rows).
Refit each spec's per-row rate through the origin against its median
real wall-clock time (not max, to avoid baking a few /ceph-contention
spikes into a rate that would then wrongly scale with dataset size),
and raised RUNTIME_SAFETY_MARGIN to compensate for that same
contention risk instead.
lars
4d6101dcd7