energy tests: hold under a host loaded past a hundred runnable threads #166

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dcharlot merged 1 commit from energy/load-robust-tests into main 2026-10-07 09:58:45 -04:00

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2026-10-05

Transaction Science

energy tests: hold under a host loaded past a hundred runnable threads ...

Two tests failed on the dev Mac, which is also the macOS CI runner, at
load averages of 101-179. Neither failure was in the meters:

- eoc-meter `the_probe_burns_its_tick_of_thread_cpu_between_samples`.
  A tick burned only 9.6 ms of the thread's CPU, under the 12.5 ms
  floor, because its 500 ms wall cap cut it short. The test's own
  message names that cap as the one thing allowed to shorten a tick,
  but the test could not tell it apart: ProbeRun recorded no tick's
  wall time. It now records each tick's wall time (`tick_walls`;
  recorded, never decided on). A tick that ran its whole wall cap is
  accepted as cut short, but only if it still spun, burning at least
  1 ms of CPU. Any other tick must burn at least half its 25 ms, as
  before.
- jouleclaw-energy `process_cpu`. The `/bin/sh` child, run for a fixed
  300 ms, got 0.076 J of CPU against a 0.2 J sanity floor (load average
  170). It failed 3 of 3 runs. The child now runs until its own counter
  reads 0.2 J (at least 300 ms, at most 5 s), as eoc-meter's equivalent
  test already does. The parent's window still spans the child's whole
  run.

Both pass at a load average of 333. Both tick mutations are caught: a
tick that sleeps through its wall cap ("ran its whole 504.6ms wall cap
and burned only 87.375µs ... it waited, not spun"), and one that sleeps
25 ms.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

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