jcp-energy: the RAPL probe tests advance their fake zones on the probe's own tick #272

Merged

dcharlot merged 1 commit from fix/rapl-probe-test-starvation into main 2026-10-16 04:39:57 -04:00

Conversation 0 Commits 1 Files changed 1 +55 -48

dcharlot commented 2026-10-15 22:35:17 -04:00

Owner

Copy link

What was wrong

Two jcp-energy tests check the RAPL liveness probe on fake powercap trees:

• the_rapl_probe_on_fake_powercap_trees
• rapl_sums_and_probes_the_package_zones_only

In both, a second thread advanced the fake zones on a 2 ms timer while the probe's tick burned CPU on the calling thread. On a loaded CI host that thread was starved, the sampling intervals went flat, and two live packages read Frozen.

It failed #270's jcp-rs leg (job 29211: "both packages advancing, psys and dram holding, was not live"), although #270 does not touch jcp.

The fix

rapl_status_ticking runs RAPL's probe with its real opener, sampler, CPU-burning tick, clock and budget. After each tick it adds the fake hardware's rise, on the probe's own thread. Every interval then sees exactly the rise the test means, so the verdict comes from the probe's rule rather than from the scheduler.

rapl_status_on, the real composition, is still exercised by the same tests' Frozen and Unavailable cases.

Checked

On the build host:

• The two tests passed in 10 of 10 runs: Live after ~311 ms while both packages rise, and Frozen at the 1 s budget while one holds.
• cargo test -p jcp-energy --features nvml passes.
• Clippy is clean.

🤖 Generated with Claude Code

## What was wrong Two jcp-energy tests check the RAPL liveness probe on fake powercap trees: - `the_rapl_probe_on_fake_powercap_trees` - `rapl_sums_and_probes_the_package_zones_only` In both, a second thread advanced the fake zones on a 2 ms timer while the probe's tick burned CPU on the calling thread. On a loaded CI host that thread was starved, the sampling intervals went flat, and two live packages read **Frozen**. It failed #270's jcp-rs leg (job 29211: "both packages advancing, psys and dram holding, was not live"), although #270 does not touch jcp. ## The fix `rapl_status_ticking` runs RAPL's probe with its real opener, sampler, CPU-burning tick, clock and budget. After each tick it adds the fake hardware's rise, on the probe's own thread. Every interval then sees exactly the rise the test means, so the verdict comes from the probe's rule rather than from the scheduler. `rapl_status_on`, the real composition, is still exercised by the same tests' Frozen and Unavailable cases. ## Checked On the build host: - The two tests passed in 10 of 10 runs: Live after ~311 ms while both packages rise, and Frozen at the 1 s budget while one holds. - `cargo test -p jcp-energy --features nvml` passes. - Clippy is clean. 🤖 Generated with [Claude Code](https://claude.com/claude-code)

dcharlot added 1 commit 2026-10-15 22:35:18 -04:00

jcp-energy: the RAPL probe tests advance their fake zones on the probe's own tick ... 8e41b48e36

Two tests checked the RAPL liveness probe on fake powercap trees:
`the_rapl_probe_on_fake_powercap_trees` and
`rapl_sums_and_probes_the_package_zones_only`. A second thread advanced the
fake zones on a 2 ms timer while the probe's tick burned CPU on the
calling thread. On a loaded CI host that thread was starved, the intervals
went flat, and two live packages read Frozen. It failed PR #270's jcp-rs
leg (job 29211: "both packages advancing, psys and dram holding, was not
live"), and that PR does not touch jcp.

`rapl_status_ticking` runs RAPL's probe with its real opener, sampler,
CPU-burning tick, clock and budget, and adds the fake hardware's rise after
each tick, on the probe's own thread. Every interval sees exactly the rise
the test means, so the verdict comes from the probe's rule and not from the
scheduler. `rapl_status_on`, the real composition, is still exercised by
the same tests' Frozen and Unavailable cases.

On the build host the two tests passed in 10 of 10 runs (Live in ~311 ms,
Frozen at the 1 s budget). The full suite passes with `--features nvml`.

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

dcharlot merged commit 3f55db66f3 into main 2026-10-16 04:39:57 -04:00

dcharlot referenced this pull request from a commit 2026-10-16 04:39:59 -04:00

Merge pull request 'jcp-energy: the RAPL probe tests advance their fake zones on the probe's own tick' (#272) from fix/rapl-probe-test-starvation into main

dcharlot referenced this pull request from a commit 2026-10-18 07:19:04 -04:00

Merge remote-tracking branch 'origin/main' into wai/d2c-m7a

Sign in to join this conversation.

Reviewers

No reviewers

Labels

Clear labels

No items

No labels

Milestone

Clear milestone

No items

No milestone

Projects

Clear projects

No items

No project

Assignees

Clear assignees

No assignees

1 participant

Notifications

Subscribe

Due date

The due date is invalid or out of range. Please use the format "yyyy-mm-dd".

No due date set.

Dependencies

No dependencies set

Reference

Transaction-Science/open-standards!272

No description provided.