diff --git a/man2/sched_setaffinity.2 b/man2/sched_setaffinity.2
index 00d82e8b4..b8511ac77 100644
--- a/man2/sched_setaffinity.2
+++ b/man2/sched_setaffinity.2
@@ -172,6 +172,18 @@ is being used.
 These restrictions on the actual set of CPUs on which the thread
 will run are silently imposed by the kernel.
 
+There are various ways of determining the number of CPUs
+available on the system, including: inspecting the contents of
+.IR /proc/cpuinfo ;
+using
+.BR syconf (3)
+to obtain the values of the
+.BR _SC_NPROCESSORS_CONF
+and
+.BR _SC_NPROCESSORS_ONLN
+parameters; and inspecting the list CPU directories under
+.IR /sys/devices/system/cpu/ .
+
 .BR sched (7)
 has a description of the Linux scheduling scheme.
 .PP