Constant DEFAULT_POLL_INTERVAL_MS 

pub const DEFAULT_POLL_INTERVAL_MS: u64 = 500;

Default poll cadence when KTSTR_STALL_POLL_MS_ENV is unset / empty / 0 / unparseable. 500 ms × W=4 yields a 2 s detection latency — short enough to catch a stuck scheduler within a typical ktstr test duration, long enough that procfs reads stay O(workers) per second rather than swamping the host.