Merge pull request #2786 from f18m/affinity-scheduling-docs

Increase details in docs

doc/zmq_ctx_set.txt

@@ -64,9 +64,11 @@ ZMQ_THREAD_PRIORITY: Set scheduling priority for I/O threads
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 The 'ZMQ_THREAD_PRIORITY' argument sets scheduling priority for
 internal context's thread pool. This option is not available on windows.
-When the scheduler policy is SCHED_OTHER on Linux, the system call "nice"
-will be used to set a priority of -20 (max priority).
 Supported values for this option depend on chosen scheduling policy.
+On Linux, when the scheduler policy is SCHED_OTHER, SCHED_IDLE or SCHED_BATCH, the OS scheduler
+will not use the thread priority but rather the thread "nice value"; in such cases
+the system call "nice" will be used to set the nice value to -20 (max priority) instead of
+adjusting the thread priority (which must be zero for those scheduling policies).
 Details can be found in sched.h file, or at http://man7.org/linux/man-pages/man2/sched_setscheduler.2.html.
 This option only applies before creating any sockets on the context.
 
@@ -78,12 +80,31 @@ ZMQ_THREAD_AFFINITY: Set CPU affinity for I/O threads
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 The 'ZMQ_THREAD_AFFINITY' argument sets CPU affinity for the internal
 context's thread pool. This option is only supported on Linux.
+On Linux, each bit of the 'option_value' argument will represent an enabled
+CPU in the corresponding cpu_set_t; for example the value 0x1 will set affinity
+of all context's thread pool to CPU 0; the value 0x110 will set affinity
+of all context's thread pool to CPU 1 and 2.
 This option only applies before creating any sockets on the context.
 
 [horizontal]
 Default value:: -1
 
 
+ZMQ_THREAD_NAME_PREFIX: Set name prefix for I/O threads
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The 'ZMQ_THREAD_NAME_PREFIX' argument sets a numeric prefix to each thread
+created for the internal context's thread pool. This option is only supported on Linux.
+This option is useful to help  debugging done via "top -H" or "gdb"; in case
+multiple processes on the system are using ZeroMQ it is useful to provide through
+this context option an application-specific prefix to distinguish ZeroMQ background
+threads that belong to different processes.
+This option only applies before creating any sockets on the context.
+
+[horizontal]
+Default value:: -1
+
+
+
 ZMQ_MAX_MSGSZ: Set maximum message size
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 The 'ZMQ_MAX_MSGSZ' argument sets the maximum allowed size