Documentation

An absent metric is not zero. Queries never enable JVM-wide monitoring. fmap transforms a genuine value and preserves every non-value status:

>>> fmap (+ 1) (Available (41 :: Int))
Available 42
>>> fmap (+ 1) (Disabled :: Available Int)
Disabled
>>> map (fmap (+ 1)) [Unsupported, Disabled, Denied, Unavailable :: Available Int]
[Unsupported,Disabled,Denied,Unavailable]

Kind of thread observed by the service, not a handle to its host carrier.

Logical lock/request information is not evidence of OS pin acceptance.

Cumulative accounting for the currently executing JVM thread. Does not enable monitoring, and is not an allocation/time budget. On a platform thread these counters include other host work performed on that thread.

OS coordinate: Linux group zero plus sparse OS CPU ID; Windows processor group plus processor number. These are not GHC capability IDs.

Inspect the caller's thread and logical capability without changing its scheduling or affinity. Fields are independently sampled.

Sample the executing JVM thread's cumulative counters. This neither enables monitoring nor isolates this guest's work from other carrier work.

Initial context eligibility in dense capability order, capped by the JVM's CPU capacity. This is not a live process-affinity query. Unavailable discovery is explicit, rather than a fabricated list of CPU IDs.

Strength of the runtime's affinity mechanism. Even pinned support does not prove that a particular thread's request was accepted.

Compatibility query preserving the original API. Native GHC returns NoCpuAffinity: ordinary GHC forkOn promises a capability, not a physical CPU. This does not inspect +RTS -qa. For detailed failure status, inspect threadAffinitySupport in currentThreadInfo.

Did this registered THC fork's initial native request succeed? False also covers unavailable support or no request. Acceptance is not a bound-thread TLS guarantee, nor a promise against subsequent OS policy changes.

Like forkOn, with the child's initial native-affinity acceptance. The callback always runs, including unavailable/rejected affinity. Preserves lazy action evaluation and inherited masking. The integer is a capability index, not an OS CPU ID; advisory acceptance remains advisory.