[Sunrisepeak]

kal_task_current issued thread_selfid at every call. openkal-musl finds errno, thread-specific data and every emulated thread-local variable of an ok image through it: 1.58 million calls in one clangd --check of mcppls-clangd's freestanding acceptance case (counted on Linux with an instrumented okrun). That was the whole of clangd.okb's difference from the native clangd on the macOS arm64 runners (1.25–1.96× across six runs; the same aarch64 image runs at 1.02× on Linux arm64, where openkal-linux caches the identifier per thread). Forcing the system call per answer on Linux reproduces the direction: 851 ms → 985 ms median.

pthread_threadid_np(NULL, &id) answers the same kernel identifier from the record libSystem keeps for each thread, without entering the kernel; the system call remains for a thread that record lacks. The value is unchanged, so nothing above observes a difference but the cost. _pthread_threadid_np joins the permitted imports and port/libSystem.tbd (a name no C library in this ecosystem defines).

Co-authored-by: speak-agent 248744407+speak-agent@users.noreply.github.com