A simple app to get run times from a thread

Just a quick app to test and demonstrate how to get run times from a
specific thread on FreeBSD.

fast_cpu_time.hpp

@@ -0,0 +1,26 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Eilertsens Kodeknekkeri
+ * SPDX-FileCopyrightText: 2025 The FreeBSD Foundation
+ * SPDX-FileContributor: Harald Eilertsen <haraldei@anduin.net>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#ifndef __FAST_CPU_TIME_HPP
+#define __FAST_CPU_TIME_HPP
+
+#include <pthread.h>
+
+/**
+ * Return the combined (sys+user) runtime of the given thread.
+ *
+ * This uses the clock_gettime(2) system call with the clock id obtained from
+ * the given thread via pthread_getcpuclockid(2).
+ *
+ * It gives the total runtime of the thread in nanoseconds. This is presumably
+ * the faster way to get the runtime of a specific thread, but we do not get
+ * the user and sys times separate.
+ */
+unsigned long fast_thread_cpu_time(pthread_t thread);
+
+#endif