[#893] added documentation

doc/sphinx/arm/dhcp4-srv.rst

@@ -3737,6 +3737,36 @@ be retained on the lease.  The lease's user-context will look something like thi
     purposes.  As long as no other purpose also writes an "ISC" element to
     user-context there should not be a conflict.
 
+.. _dhcp4-multi-threading-settings:
+
+Multi-threading settings
+------------------------
+
+The Kea server can be configured to process packets in parallel using multiple
+threads. Related setting for this feature are:
+
+-  ``enable-multi-threading`` - use multiple threads to process packets in
+    parallel
+
+-  ``packet-thread-pool-size`` - specify the number of threads to process
+   packets in parallel.  Supported values are: 0 (autodetect), any positive
+   number sets number of threads explicitly.
+
+-  ``packet-thread-queue-size`` - specify the size of the queue used by each
+   thread to process packets.  Supported values are: 0 (unlimited), any positive
+   number sets size explicitly.
+
+An example configuration that sets these parameter looks as follows:
+
+::
+
+   "Dhcp4": {
+       "enable-multi-threading": true,
+       "packet-thread-pool-size": 4,
+       "packet-thread-queue-size": 16,
+       ...
+   }
+
 .. _host-reservation-v4:
 
 Host Reservation in DHCPv4

doc/sphinx/arm/dhcp6-srv.rst

@@ -3249,6 +3249,36 @@ pretty-printed for clarity):
     container serving mulitple purposes.  As long as no other purpose also
     writes an "ISC" element to user-context there should not be a conflict.
 
+.. _dhcp6-multi-threading-settings:
+
+Multi-threading settings
+------------------------
+
+The Kea server can be configured to process packets in parallel using multiple
+threads. Related setting for this feature are:
+
+-  ``enable-multi-threading`` - use multiple threads to process packets in
+    parallel
+
+-  ``packet-thread-pool-size`` - specify the number of threads to process
+   packets in parallel.  Supported values are: 0 (autodetect), any positive
+   number sets number of threads explicitly.
+
+-  ``packet-thread-queue-size`` - specify the size of the queue used by each
+   thread to process packets.  Supported values are: 0 (unlimited), any positive
+   number sets size explicitly.
+
+An example configuration that sets these parameter looks as follows:
+
+::
+
+   "Dhcp6": {
+       "enable-multi-threading": true,
+       "packet-thread-pool-size": 4,
+       "packet-thread-queue-size": 16,
+       ...
+   }
+
 .. _host-reservation-v6:
 
 Host Reservation in DHCPv6

src/bin/dhcp4/dhcp4_srv.h

@@ -1062,9 +1062,9 @@ protected:
 
 public:
     /// @brief command line parameter thread count
-    /// when parameter is not specified, the default value is used
+    /// when parameter is not specified, the default value -1 is used
-    /// the default value is: -1 means disabled (single-threaded),
+    /// which means disabled (single-threaded), 0 means auto-detect, other
-    /// 0 means auto-detect, other values set thread count explicitly
+    /// values set thread count explicitly.
     static int srv_thread_count_;
 
     /// Class methods for DHCPv4-over-DHCPv6 handler

src/bin/dhcp6/dhcp6_srv.h

@@ -1062,9 +1062,9 @@ protected:
 
 public:
     /// @brief command line parameter thread count
-    /// when parameter is not specified, the default value is used
+    /// when parameter is not specified, the default value -1 is used
-    /// the default value is: -1 means disabled (single-threaded),
+    /// which means disabled (single-threaded), 0 means auto-detect, other
-    /// 0 means auto-detect, other values set thread count explicitly
+    /// values set thread count explicitly.
     static int srv_thread_count_;
 
     /// @note used by DHCPv4-over-DHCPv6 so must be public and static

src/lib/dhcpsrv/srv_config.cc

@@ -443,7 +443,15 @@ SrvConfig::toElement() const {
     // Set dhcp4o6-port
     dhcp->set("dhcp4o6-port",
               Element::create(static_cast<int>(dhcp4o6_port_)));
-
+    // Set enable-multi-threading
+    dhcp->set("enable-multi-threading",
+             Element::create(enable_multi_threading_));
+    // Set packet-thread-pool-size
+    dhcp->set("packet-thread-pool-size",
+             Element::create(static_cast<int>(pkt_thread_pool_size_)));
+    // Set packet-thread-queue-size
+    dhcp->set("packet-thread-queue-size",
+             Element::create(static_cast<int>(pkt_thread_queue_size_)));
     // Set dhcp-ddns
     dhcp->set("dhcp-ddns", d2_client_config_->toElement());
     // Set interfaces-config