-/* True on systems (particularly x86-64 Linux) where clock_gettime() is
- * inexpensive. On these systems, we don't bother caching the current time.
- * Instead, we consult clock_gettime() directly when needed.
- *
- * False on systems where clock_gettime() is relatively expensive. On these
- * systems, we cache the current time and set up a periodic SIGALRM to remind
- * us to update it.
- *
- * Also false on systems (e.g. ESX) that don't support setting up timers based
- * on a monotonically increasing clock. */
+/* True on systems that support a monotonic clock. Compared to just getting
+ * the value of a variable, clock_gettime() is somewhat expensive, even on
+ * systems that try hard to optimize it (such as x86-64 Linux), so it's
+ * worthwhile to minimize calls via caching. */