# cpu
cpu utility
## features
- thread affinity for current or selected linux thread ids
- online cpu counting and iteration
- physical core counting
- cache line padding
- atomic cursor helpers
- cpu pause, fences, and prefetch helpers
- spin, yield, and backoff wait strategies
## affinity
use `set_current_thread_affinity` when a worker pins itself during startup.
use `current_thread_id` and `set_cpu_affinity` when the caller owns the target thread id.
## hot path
cursor, fence, prefetch, cache padding, and wait strategy operations avoid heap allocation.
affinity and topology calls are cold path setup operations and may read sysfs or call the kernel.