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-rw-r--r--erts/doc/src/Makefile2
-rw-r--r--erts/doc/src/alt_dist.xml736
-rw-r--r--erts/doc/src/erl.xml42
-rw-r--r--erts/doc/src/erl_dist_protocol.xml70
-rw-r--r--erts/doc/src/erlang.xml177
-rw-r--r--erts/doc/src/notes.xml8
6 files changed, 964 insertions, 71 deletions
diff --git a/erts/doc/src/Makefile b/erts/doc/src/Makefile
index b96cbbce40..444adf4a6e 100644
--- a/erts/doc/src/Makefile
+++ b/erts/doc/src/Makefile
@@ -173,6 +173,8 @@ release_docs_spec: docs
"$(RELSYSDIR)/doc/html"
$(INSTALL_DATA) $(ERL_TOP)/erts/example/time_compat.erl \
"$(RELSYSDIR)/doc/html"
+ $(INSTALL_DATA) $(ERL_TOP)/lib/kernel/examples/gen_tcp_dist/src/gen_tcp_dist.erl \
+ "$(RELSYSDIR)/doc/html"
$(INSTALL_DATA) $(INFO_FILE) "$(RELSYSDIR)"
$(INSTALL_DIR) "$(RELEASE_PATH)/man/man3"
$(INSTALL_DATA) $(MAN3DIR)/* "$(RELEASE_PATH)/man/man3"
diff --git a/erts/doc/src/alt_dist.xml b/erts/doc/src/alt_dist.xml
index be969a8267..d3731a5391 100644
--- a/erts/doc/src/alt_dist.xml
+++ b/erts/doc/src/alt_dist.xml
@@ -47,23 +47,30 @@
runs on. The reason the C code is not made portable, is simply
readability.</p>
- <note>
- <p>This section was written a long time ago. Most of it is still
- valid, but some things have changed since then.
- Most notably is the driver interface. Some updates have been made
- to the documentation of the driver presented here,
- but more can be done and is planned for the future.
- The reader is encouraged to read the
- <seealso marker="erl_driver"><c>erl_driver</c></seealso> and
- <seealso marker="driver_entry"><c>driver_entry</c></seealso>
- documentation also.</p>
- </note>
-
<section>
<title>Introduction</title>
<p>To implement a new carrier for the Erlang distribution, the main
steps are as follows.</p>
+ <note><p>
+ As of ERTS version 10.0 support for distribution controller
+ processes has been introduced. That is, the traffic over a
+ distribution channel can be managed by a process instead of
+ only by a port. This makes it possible to implement large
+ parts of the logic in Erlang code, and you perhaps do not
+ even need a new driver for the protocol. One example could
+ be Erlang distribution over UDP using <c>gen_udp</c> (your
+ Erlang code will of course have to take care of retranspissions,
+ etc in this example). That is, depending on what you want
+ to do you perhaps do not need to implement a driver at all
+ and can then skip the driver related sections below.
+ The <c>gen_tcp_dist</c> example described in the
+ <seealso marker="#distribution_module">Distribution
+ Module</seealso> section utilize distribution controller
+ processes and can be worth having a look at if you want to
+ use distribution controller processes.
+ </p></note>
+
<section>
<title>Writing an Erlang Driver</title>
<p>First, the protocol must be available to the Erlang machine, which
@@ -152,7 +159,712 @@
</section>
<section>
+ <marker id="distribution_module"/>
+ <title>Distribution Module</title>
+ <p>
+ The distribution module expose an API that <c>net_kernel</c> call
+ in order to manage connections to other nodes. The module name
+ should have the suffix <c>_dist</c>.
+ </p>
+ <p>
+ The module needs to create some kind of listening entity (process
+ or port) and an acceptor process that accepts incoming connections
+ using the listening entity. For each connection, the module at least
+ needs to create one connection supervisor process, which also is
+ responsible for the handshake when setting up the connection, and
+ a distribution controller (process or port) responsible for
+ transport of data over the connection. The distribution controller
+ and the connection supervisor process should be linked together
+ so both of them are cleaned up when the connection is taken down.
+ </p>
+ <p>
+ Note that there need to be exactly one distribution controller
+ per connection. A process or port can only be distribution
+ controller for one connection. The registration as distribution
+ controller cannot be undone. It will stick until the distribution
+ controller terminates. The distribution controller should not
+ ignore exit signals. It is allowed to trap exits, but it should
+ then voluntarily terminate when an exit signal is received.
+ </p>
+ <p>
+ An example implementation of a distribution module can be found
+ in
+ <url href="gen_tcp_dist.erl">$ERL_TOP/lib/kernel/examples/gen_tcp_dist/src/gen_tcp_dist.erl</url>.
+ It implements the distribution over TCP/IP using the <c>gen_tcp</c>
+ API with distribution controllers implemented by processes. This
+ instead of using port distribution controllers as the ordinary TCP/IP
+ distribution uses.
+ </p>
+
+ <section>
+ <marker id="distribution_module_exported_callback_functions"/>
+ <title>Exported Callback Functions</title>
+
+ <p>
+ The following functions are mandatory:
+ </p>
+ <taglist>
+ <tag><marker id="listen"/><c>listen(Name) -></c><br/>&nbsp;&nbsp;<c>{ok, {Listen, Address, Creation}} | {error, Error} </c></tag>
+ <item>
+ <p>
+ <c>listen/1</c> is called once in order to listen for incoming
+ connection requests. The call is made when the distribution is brought
+ up. The argument <c>Name</c> is the part of the node name before
+ the <c>@</c> sign in the full node name. It can be either an atom or a
+ string.
+ </p>
+ <p>
+ The return value consists of a <c>Listen</c> handle (which is
+ later passed to the <seealso marker="#accept"><c>accept/1</c></seealso>
+ callback), <c>Address</c> which is a <c>#net_address{}</c> record
+ with information about the address for the node (the
+ <c>#net_address{}</c> record is defined in
+ <c>kernel/include/net_address.hrl</c>), and <c>Creation</c> which
+ (currently) is an integer <c>1</c>, <c>2</c>, or <c>3</c>.
+ </p>
+ <p>
+ If <seealso marker="erts:epmd"><c>epmd</c></seealso> is to be used
+ for node discovery, you typically want to use the (unfortunately
+ undocumented) <c>erl_epmd</c> module (part of the <c>kernel</c>
+ application) in order to register the listen port with <c>epmd</c>
+ and retrieve <c>Creation</c> to use.
+ </p>
+ </item>
+
+ <tag><marker id="accept"/><c>accept(Listen) -></c><br/>&nbsp;&nbsp;<c>AcceptorPid</c></tag>
+ <item>
+ <p>
+ <c>accept/1</c> should spawn a process that accepts connections. This
+ process should preferably execute on <c>max</c> priority. The process
+ identifier of this process should be returned.
+ </p>
+ <p>
+ The <c>Listen</c> argument will be the same as the <c>Listen</c> handle
+ part of the return value of the
+ <seealso marker="#listen"><c>listen/1</c></seealso> callback above.
+ <c>accept/1</c> is called only once when the distribution protocol is
+ started.
+ </p>
+ <p>
+ The caller of this function is a representative for <c>net_kernel</c>
+ (this may or may not be the process registered as <c>net_kernel</c>)
+ and is in this document identified as <c>Kernel</c>.
+ When a connection has been accepted by the acceptor process, it needs
+ to inform <c>Kernel</c> about the accepted connection. This is done by
+ passing a message on the form:
+ </p>
+ <code type="none"><![CDATA[Kernel ! {accept, AcceptorPid, DistController, Family, Proto}]]></code>
+ <p>
+ <c>DistController</c> is either the process or port identifier
+ of the distribution controller for the connection. The
+ distribution controller should be created by the acceptor
+ processes when a new connection is accepted. Its job is to
+ dispatch traffic on the connection.
+ </p>
+ <c>Kernel</c> responds with one of the following messages:
+ <taglist>
+ <tag><c>{Kernel, controller, SupervisorPid}</c></tag>
+ <item>
+ <p>
+ The request was accepted and <c>SupervisorPid</c> is the
+ process identifier of the connection supervisor process
+ (which is created in the
+ <seealso marker="#accept_connection"><c>accept_connection/5</c></seealso>
+ callback).
+ </p>
+ </item>
+ <tag><c>{Kernel, unsupported_protocol}</c></tag>
+ <item>
+ <p>
+ The request was rejected. This is a fatal error. The acceptor
+ process should terminate.
+ </p>
+ </item>
+ </taglist>
+ <p>
+ When an accept sequence has been completed the acceptor process
+ is expected to continue accepting further requests.
+ </p>
+ </item>
+
+ <tag><marker id="accept_connection"/><c>accept_connection(AcceptorPid, DistCtrl, MyNode, Allowed, SetupTime) -></c><br/>&nbsp;&nbsp;<c>ConnectionSupervisorPid</c></tag>
+ <item>
+ <p>
+ <c>accept_connection/5</c> should spawn a process that will
+ perform the Erlang distribution handshake for the connection.
+ If the handshake successfully completes it should continue to
+ function as a connection supervisor. This process
+ should preferably execute on <c>max</c> priority.
+ </p>
+ <p>The arguments:</p>
+ <taglist>
+ <tag><c>AcceptorPid</c></tag>
+ <item>
+ <p>
+ Process identifier of the process created by the
+ <seealso marker="#accept"><c>accept/1</c></seealso>
+ callback.
+ </p>
+ </item>
+ <tag><c>DistCtrl</c></tag>
+ <item>
+ <p>The identifier of the distribution controller identifier
+ created by the acceptor process. To be passed along to
+ <c>dist_util:handshake_other_started(HsData)</c>.
+ </p>
+ </item>
+ <tag><c>MyNode</c></tag>
+ <item>
+ <p>
+ Node name of this node. To be passed along to
+ <c>dist_util:handshake_other_started(HsData)</c>.
+ </p>
+ </item>
+ <tag><c>Allowed</c></tag>
+ <item>
+ <p>
+ To be passed along to
+ <c>dist_util:handshake_other_started(HsData)</c>.
+ </p>
+ </item>
+ <tag><c>SetupTime</c></tag>
+ <item>
+ <p>
+ Time used for creating a setup timer by a
+ call to <c>dist_util:start_timer(SetupTime)</c>.
+ The timer should be passed along to
+ <c>dist_util:handshake_other_started(HsData)</c>.
+ </p>
+ </item>
+ </taglist>
+ <p>
+ The created process should provide callbacks and other
+ information needed for the handshake in a
+ <seealso marker="#hs_data_record"><c>#hs_data{}</c></seealso>
+ record and call <c>dist_util:handshake_other_started(HsData)</c>
+ with this record.
+ </p>
+ <p>
+ <c>dist_util:handshake_other_started(HsData)</c> will perform
+ the handshake and if the handshake successfully completes this
+ process will then continue in a connection supervisor loop
+ as long as the connection is up.
+ </p>
+ </item>
+
+ <tag><marker id="setup"/><c>setup(Node, Type, MyNode, LongOrShortNames, SetupTime) -></c><br/>&nbsp;&nbsp;<c>ConnectionSupervisorPid</c></tag>
+ <item>
+ <p>
+ <c>setup/5</c> should spawn a process that connects to
+ <c>Node</c>. When connection has been established it should
+ perform the Erlang distribution handshake for the connection.
+ If the handshake successfully completes it should continue to
+ function as a connection supervisor. This process
+ should preferably execute on <c>max</c> priority.
+ </p>
+ <p>The arguments:</p>
+ <taglist>
+ <tag><c>Node</c></tag>
+ <item>
+ <p>
+ Node name of remote node. To be passed along to
+ <c>dist_util:handshake_we_started(HsData)</c>.
+ </p>
+ </item>
+ <tag><c>Type</c></tag>
+ <item>
+ <p>
+ Connection type. To be passed along to
+ <c>dist_util:handshake_we_started(HsData)</c>.
+ </p>
+ </item>
+ <tag><c>MyNode</c></tag>
+ <item>
+ <p>
+ Node name of this node. To be passed along to
+ <c>dist_util:handshake_we_started(HsData)</c>.
+ </p>
+ </item>
+ <tag><c>LongOrShortNames</c></tag>
+ <item>
+ <p>
+ Either the atom <c>longnames</c> or
+ the atom <c>shortnames</c> indicating
+ whether long or short names is used.
+ </p>
+ </item>
+ <tag><c>SetupTime</c></tag>
+ <item>
+ <p>
+ Time used for creating a setup timer by a
+ call to <c>dist_util:start_timer(SetupTime)</c>.
+ The timer should be passed along to
+ <c>dist_util:handshake_we_started(HsData)</c>.
+ </p>
+ </item>
+ </taglist>
+ <p>
+ The caller of this function is a representative for <c>net_kernel</c>
+ (this may or may not be the process registered as <c>net_kernel</c>)
+ and is in this document identified as <c>Kernel</c>.
+ </p>
+ <p>
+ This function should, besides spawning the connection supervisor,
+ also create a distribution controller. The distribution
+ controller is either a process or a port which is responsible
+ for dispatching traffic.
+ </p>
+ <p>
+ The created process should provide callbacks and other
+ information needed for the handshake in a
+ <seealso marker="#hs_data_record"><c>#hs_data{}</c></seealso>
+ record and call <c>dist_util:handshake_we_started(HsData)</c>
+ with this record.
+ </p>
+ <p>
+ <c>dist_util:handshake_we_started(HsData)</c> will perform
+ the handshake and the handshake successfully completes this
+ process will then continue in a connection supervisor loop
+ as long as the connection is up.
+ </p>
+ </item>
+
+ <tag><marker id="close"/><c>close(Listen) -></c><br/>&nbsp;&nbsp;<c>void()</c></tag>
+
+ <item><p>
+ Called in order to close the <c>Listen</c> handle
+ that originally was passed from the
+ <seealso marker="#listen"><c>listen/1</c></seealso> callback.
+ </p></item>
+
+ <tag><marker id="select"/><c>select(NodeName) -></c><br/>&nbsp;&nbsp;<c>boolean()</c></tag>
+ <item>
+ <p>Return <c>true</c> if the host name part
+ of the <c>NodeName</c> is valid for use
+ with this protocol; otherwise, <c>false</c>.
+ </p>
+ </item>
+
+ </taglist>
+
+ <p>
+ There are also two optional functions that may be
+ exported:
+ </p>
+ <taglist>
+ <tag><marker id="select"/><c>setopts(Listen, Opts) -></c><br/>&nbsp;&nbsp;<c>ok | {error, Error}</c></tag>
+ <item>
+ <p>
+ The argument <c>Listen</c> is the handle originally passed
+ from the
+ <seealso marker="#listen"><c>listen/1</c></seealso> callback.
+ The argument <c>Opts</c> is a list of options to set on future
+ connections.
+ </p>
+ </item>
+
+ <tag><marker id="select"/><c>getopts(Listen, Opts) -></c><br/>&nbsp;&nbsp;<c>{ok, OptionValues} | {error, Error}</c></tag>
+ <item>
+ <p>
+ The argument <c>Listen</c> is the handle originally passed
+ from the
+ <seealso marker="#listen"><c>listen/1</c></seealso> callback.
+ The argument <c>Opts</c> is a list of options to read for future
+ connections.
+ </p>
+ </item>
+ </taglist>
+
+ </section>
+ <section>
+ <marker id="hs_data_record"/>
+ <title>The #hs_data{} Record</title>
+ <p>
+ The <c>dist_util:handshake_we_started/1</c> and
+ <c>dist_util:handshake_other_started/1</c> functions
+ takes a <c>#hs_data{}</c> record as argument. There
+ are quite a lot of fields in this record that you
+ need to set. The record is defined in
+ <c>kernel/include/dist_util.hrl</c>. Not documented
+ fields should not be set, i.e., should be left as
+ <c>undefined</c>.
+ </p>
+ <p>
+ The following <c>#hs_data{}</c> record fields need
+ to be set unless otherwise stated:</p>
+ <taglist>
+ <tag><marker id="hs_data_kernel_pid"/><c>kernel_pid</c></tag>
+ <item>
+ <p>
+ Process identifier of the <c>Kernel</c> process. That is,
+ the process that called either
+ <seealso marker="#setup"><c>setup/5</c></seealso> or
+ <seealso marker="#accept_connection"><c>accept_connection/5</c></seealso>.
+ </p>
+ </item>
+
+ <tag><marker id="hs_data_other_node"/><c>other_node</c></tag>
+ <item>
+ <p>Name of the other node. This field is only
+ mandatory when this node initiates the connection.
+ That is, when connection is set up via
+ <seealso marker="#setup"><c>setup/5</c></seealso>.
+ </p>
+ </item>
+
+ <tag><marker id="hs_data_this_node"/><c>this_node</c></tag>
+ <item>
+ <p>
+ The node name of this node.
+ </p>
+ </item>
+
+ <tag><marker id="hs_data_socket"/><c>socket</c></tag>
+ <item>
+ <p>
+ The identifier of the distribution controller.
+ </p>
+ </item>
+
+ <tag><marker id="hs_data_timer"/><c>timer</c></tag>
+ <item>
+ <p>
+ The timer created using <c>dist_util:start_timer/1</c>.
+ </p>
+ </item>
+
+ <tag><marker id="hs_data_allowed"/><c>allowed</c></tag>
+ <item>
+ <p>Information passed as <c>Allowed</c> to
+ <c>accept_connection/5</c>. This field is only
+ mandatory when the remote node initiated the
+ connection. That is, when the connection is set
+ up via
+ <seealso marker="#accept_connection"><c>accept_connection/5</c></seealso>.
+ </p>
+ </item>
+
+ <tag><marker id="hs_data_f_send"/><c>f_send</c></tag>
+ <item>
+ <p>
+ A fun with the following signature:
+ </p>
+ <code type="none"><![CDATA[fun (DistCtrlr, Data) -> ok | {error, Error}]]></code>
+ <p>
+ where <c>DistCtrlr</c> is the identifier of
+ the distribution controller and <c>Data</c>
+ is io data to pass to the other side.
+ </p>
+ <p>Only used during handshake phase.</p>
+ </item>
+
+ <tag><marker id="hs_data_f_recv"/><c>f_recv</c></tag>
+ <item>
+ <p>
+ A fun with the following signature:
+ </p>
+ <code type="none"><![CDATA[fun (DistCtrlr, Length) -> {ok, Packet} | {error, Reason}]]></code>
+ <p>
+ where <c>DistCtrlr</c> is the identifier of the distribution
+ controller.
+ If <c>Length</c> is <c>0</c>, all available bytes should be
+ returned. If <c>Length > 0</c>, exactly <c>Length</c> bytes
+ should be returned, or an error; possibly discarding less
+ than <c>Length</c> bytes of data when the connection is
+ closed from the other side.
+ It is used for passive receive of data from the
+ other end.
+ </p>
+ <p>Only used during handshake phase.</p>
+ </item>
+
+ <tag><marker id="hs_data_f_setopts_pre_nodeup"/><c>f_setopts_pre_nodeup</c></tag>
+ <item>
+ <p>
+ A fun with the following signature:
+ </p>
+ <code type="none"><![CDATA[fun (DistCtrlr) -> ok | {error, Error}]]></code>
+ <p>
+ where <c>DistCtrlr</c> is the identifier of
+ the distribution controller. Called just
+ before the distribution channel is taken up
+ for normal traffic.
+ </p>
+ <p>Only used during handshake phase.</p>
+ </item>
+
+ <tag><marker id="hs_data_f_setopts_post_nodeup"/><c>f_setopts_post_nodeup</c></tag>
+ <item>
+ <p>
+ A fun with the following signature:
+ </p>
+ <code type="none"><![CDATA[fun (DistCtrlr) -> ok | {error, Error}]]></code>
+ <p>
+ where <c>DistCtrlr</c> is the identifier of
+ the distribution controller. Called just
+ after distribution channel has been taken
+ up for normal traffic.
+ </p>
+ <p>Only used during handshake phase.</p>
+ </item>
+
+ <tag><marker id="hs_data_f_getll"/><c>f_getll</c></tag>
+ <item>
+ <p>
+ A fun with the following signature:
+ </p>
+ <code type="none"><![CDATA[fun (DistCtrlr) -> ID]]></code>
+ <p>
+ where <c>DistCtrlr</c> is the identifier of
+ the distribution controller and <c>ID</c> is
+ the identifier of the low level entity that
+ handles the connection (often <c>DistCtrlr</c>
+ itself).
+ </p>
+ <p>Only used during handshake phase.</p>
+ </item>
+
+ <tag><marker id="hs_data_f_address"/><c>f_address</c></tag>
+ <item>
+ <p>
+ A fun with the following signature:
+ </p>
+ <code type="none"><![CDATA[fun (DistCtrlr, Node) -> NetAddress]]></code>
+ <p>
+ where <c>DistCtrlr</c> is the identifier of
+ the distribution controller, <c>Node</c>
+ is the node name of the node on the other end,
+ and <c>NetAddress</c> is a <c>#net_address{}</c>
+ record with information about the address
+ for the <c>Node</c> on the other end of the
+ connection. The <c>#net_address{}</c> record
+ is defined in
+ <c>kernel/include/net_address.hrl</c>.
+ </p>
+ <p>Only used during handshake phase.</p>
+ </item>
+
+ <tag><marker id="hs_data_mf_tick"/><c>mf_tick</c></tag>
+ <item>
+ <p>
+ A fun with the following signature:
+ </p>
+ <code type="none"><![CDATA[fun (DistCtrlr) -> void()]]></code>
+ <p>
+ where <c>DistCtrlr</c> is the identifier
+ of the distribution controller. This
+ function should send information over
+ the connection that is not interpreted
+ by the other end while increasing the
+ statistics of received packets on the
+ other end. This is usually implemented by
+ sending an empty packet.
+ </p>
+ <note><p>
+ It is of vital importance that this operation
+ does not block the caller for a long time.
+ This since it is called from the connection
+ supervisor.
+ </p></note>
+ <p>Used when connection is up.</p>
+ </item>
+
+ <tag><marker id="hs_data_mf_getstat"/><c>mf_getstat</c></tag>
+ <item>
+ <p>
+ A fun with the following signature:
+ </p>
+ <code type="none"><![CDATA[fun (DistCtrlr) -> {ok, Received, Sent, PendSend}]]></code>
+ <p>
+ where <c>DistCtrlr</c> is the identifier
+ of the distribution controller, <c>Received</c>
+ is received packets, <c>Sent</c> is
+ sent packets, and <c>PendSend</c> is
+ amount of packets in queue to be sent
+ or a <c>boolean()</c> indicating whether
+ there are packets in queue to be sent.
+ </p>
+ <note><p>
+ It is of vital importance that this operation
+ does not block the caller for a long time.
+ This since it is called from the connection
+ supervisor.
+ </p></note>
+ <p>Used when connection is up.</p>
+ </item>
+
+ <tag><marker id="hs_data_request_type"/><c>request_type</c></tag>
+ <item>
+ <p>
+ The request <c>Type</c> as passed to
+ <seealso marker="#setup"><c>setup/5</c></seealso>.
+ This is only mandatory when the connection has
+ been initiated by this node. That is, the connection
+ is set up via <c>setup/5</c>.
+ </p>
+ </item>
+
+ <tag><marker id="hs_data_mf_setopts"/><c>mf_setopts</c></tag>
+ <item>
+ <p>
+ A fun with the following signature:
+ </p>
+ <code type="none"><![CDATA[fun (DistCtrl, Opts) -> ok | {error, Error}]]></code>
+ <p>
+ where <c>DistCtrlr</c> is the identifier
+ of the distribution controller and <c>Opts</c>
+ is a list of options to set on the connection.
+ </p>
+ <p>This function is optional. Used when connection is up.</p>
+ </item>
+
+ <tag><marker id="hs_data_mf_getopts"/><c>mf_getopts</c></tag>
+ <item>
+ <p>
+ A fun with the following signature:
+ </p>
+ <code type="none"><![CDATA[fun (DistCtrl, Opts) -> {ok, OptionValues} | {error, Error}]]></code>
+ <p>
+ where <c>DistCtrlr</c> is the identifier
+ of the distribution controller and <c>Opts</c>
+ is a list of options to read for the connection.
+ </p>
+ <p>This function is optional. Used when connection is up.</p>
+ </item>
+
+ <tag><marker id="hs_data_f_handshake_complete"/><c>f_handshake_complete</c></tag>
+ <item>
+ <p>
+ A fun with the following signature:
+ </p>
+ <code type="none"><![CDATA[fun (DistCtrlr, Node, DHandle) -> void()]]></code>
+ <p>
+ where <c>DistCtrlr</c> is the identifier
+ of the distribution controller, <c>Node</c> is
+ the node name of the node connected at the other
+ end, and <c>DHandle</c> is a distribution handle
+ needed by a distribution controller process when
+ calling the following BIFs:
+ </p>
+ <list>
+ <item><p><seealso marker="erts:erlang#dist_ctrl_get_data/1"><c>erlang:dist_ctrl_get_data/1</c></seealso></p></item>
+ <item><p><seealso marker="erts:erlang#dist_ctrl_get_data_notification/1"><c>erlang:dist_ctrl_get_data_notification/1</c></seealso></p></item>
+ <item><p><seealso marker="erts:erlang#dist_ctrl_input_handler/2"><c>erlang:dist_ctrl_input_handler/2</c></seealso></p></item>
+ <item><p><seealso marker="erts:erlang#dist_ctrl_put_data/2"><c>erlang:dist_ctrl_put_data/2</c></seealso></p></item>
+ </list>
+ <p>
+ This function is called when the handshake has
+ completed and the distribution channel is up.
+ The distribution controller can begin dispatching
+ traffic over the channel. This function is optional.
+ </p>
+ <p>Only used during handshake phase.</p>
+ </item>
+
+ <tag><marker id="hs_data_add_flags"/><c>add_flags</c></tag>
+ <item>
+ <p>
+ <seealso marker="erl_dist_protocol#dflags">Distribution flags</seealso>
+ to add to the connection. Currently all (non obsolete) flags will
+ automatically be enabled.
+ </p>
+ <p>
+ This flag field is optional.
+ </p>
+ </item>
+
+ <tag><marker id="hs_data_reject_flags"/><c>reject_flags</c></tag>
+ <item>
+ <p>
+ <seealso marker="erl_dist_protocol#dflags">Distribution flags</seealso>
+ to reject. Currently the following distribution flags can be rejected:
+ </p>
+ <taglist>
+ <tag><c>DFLAG_DIST_HDR_ATOM_CACHE</c></tag>
+ <item>Do not use atom cache over this connection.</item>
+ <tag><c>DFLAGS_STRICT_ORDER_DELIVERY</c></tag>
+ <item>Do not use any features that require strict
+ order delivery.</item>
+ </taglist>
+ <p>
+ This flag field is optional.
+ </p>
+ </item>
+
+ <tag><marker id="hs_data_require_flags"/><c>require_flags</c></tag>
+ <item>
+ <p>
+ Require these <seealso marker="erl_dist_protocol#dflags">distribution
+ flags</seealso> to be used. The connection will be aborted during the
+ handshake if the other end does not use them.
+ </p>
+ <p>
+ This flag field is optional.
+ </p>
+ </item>
+
+ </taglist>
+ </section>
+
+ <section>
+ <marker id="distribution_data_delivery"/>
+ <title>Distribution Data Delivery</title>
+ <p>
+ When using the default configuration, the data to pass
+ over a connection needs to be delivered as is
+ to the node on the receiving end in the <em>exact same
+ order</em>, with no loss of data what so ever, as sent
+ from the sending node.
+ </p>
+ <p>
+ The data delivery order can be relaxed by disabling
+ features that require strict ordering. This is done by
+ passing the <c>?DFLAGS_STRICT_ORDER_DELIVERY</c>
+ <seealso marker="erl_dist_protocol#dflags">distribution
+ flags</seealso> in the
+ <seealso marker="alt_dist#hs_data_reject_flags"><c>reject_flags</c></seealso>
+ field of the <seealso marker="#hs_data_record"><c>#hs_data{}</c></seealso>
+ record used when setting up the connection. When relaxed
+ ordering is used, only the order of signals with the same
+ sender/receiver pair has to be preserved.
+ However, note that disabling the features that require
+ strict ordering may have a negative impact on performance,
+ throughput, and/or latency.
+ </p>
+ </section>
+
+ <section>
+ <marker id="enable_your_distribution_module"/>
+ <title>Enable Your Distribution Module</title>
+
+ <p>For <c>net_kernel</c> to find out which distribution module to use,
+ the <c>erl</c> command-line argument <c>-proto_dist</c> is used. It
+ is followed by one or more distribution module names, with suffix
+ "_dist" removed. That is, <c>gen_tcp_dist</c> as a distribution module
+ is specified as <c>-proto_dist gen_tcp</c>.</p>
+
+ <p>If no <c>epmd</c> (TCP port mapper daemon) is used, also command-line
+ option <c>-no_epmd</c> is to be specified, which makes
+ Erlang skip the <c>epmd</c> startup, both as an OS process and as an
+ Erlang ditto.</p>
+ </section>
+
+ </section>
+
+ <section>
<title>The Driver</title>
+
+ <note>
+ <p>This section was written a long time ago. Most of it is still
+ valid, but some things have changed since then. Some updates have
+ been made to the documentation of the driver presented here,
+ but more can be done and is planned for the future.
+ The reader is encouraged to read the
+ <seealso marker="erl_driver"><c>erl_driver</c></seealso> and
+ <seealso marker="driver_entry"><c>driver_entry</c></seealso>
+ documentation also.</p>
+ </note>
+
<p>Although Erlang drivers in general can be beyond the scope of this
section, a brief introduction seems to be in place.</p>
diff --git a/erts/doc/src/erl.xml b/erts/doc/src/erl.xml
index 638e88ca31..71fe08d4e6 100644
--- a/erts/doc/src/erl.xml
+++ b/erts/doc/src/erl.xml
@@ -538,20 +538,6 @@
<p>Note that a distributed node will fail to start if epmd is
not running.</p>
</item>
- <tag><marker id="smp"/><c><![CDATA[-smp [enable|auto|disable]]]></c></tag>
- <item>
- <p><c>-smp enable</c> and <c>-smp</c> start the Erlang runtime
- system with SMP support enabled. This can fail if no runtime
- system with SMP support is available. <c>-smp auto</c> starts
- the Erlang runtime system with SMP support enabled if it is
- available and more than one logical processor is detected.
- <c>-smp disable</c> starts a runtime system without SMP support.
- The runtime system without SMP support is deprecated and will
- be removed in a future major release.</p>
- <note>
- <p>See also flag<seealso marker="#+S"><c>+S</c></seealso>.</p>
- </note>
- </item>
<tag><c><![CDATA[-version]]></c> (emulator flag)</tag>
<item>
<p>Makes the emulator print its version number. The same
@@ -902,7 +888,7 @@
<c><![CDATA[+S Schedulers:SchedulerOnline]]></c></tag>
<item>
<p>Sets the number of scheduler threads to create and scheduler threads
- to set online when SMP support has been enabled. The maximum for both
+ to set online. The maximum for both
values is 1024. If the Erlang runtime system is able to determine the
number of logical processors configured and logical processors
available, <c>Schedulers</c> defaults to logical processors
@@ -920,8 +906,6 @@
<p>Specifying value <c>0</c> for <c>Schedulers</c> or
<c>SchedulersOnline</c> resets the number of scheduler threads or
scheduler threads online, respectively, to its default value.</p>
- <p>This option is ignored if the emulator does not have SMP support
- enabled (see flag <seealso marker="#smp"><c>-smp</c></seealso>).</p>
</item>
<tag><marker id="+SP"/><c><![CDATA[+SP
SchedulersPercentage:SchedulersOnlinePercentage]]></c></tag>
@@ -929,8 +913,8 @@
<p>Similar to <seealso marker="#+S"><c>+S</c></seealso> but uses
percentages to set the number of scheduler threads to create, based
on logical processors configured, and scheduler threads to set online,
- based on logical processors available, when SMP support has been
- enabled. Specified values must be &gt; 0. For example,
+ based on logical processors available.
+ Specified values must be &gt; 0. For example,
<c>+SP 50:25</c> sets the number of scheduler threads to 50% of the
logical processors configured, and the number of scheduler threads
online to 25% of the logical processors available.
@@ -945,15 +929,13 @@
and 8 logical cores available, the combination of the options
<c>+S 4:4 +SP 50:25</c> (in either order) results in 2 scheduler
threads (50% of 4) and 1 scheduler thread online (25% of 4).</p>
- <p>This option is ignored if the emulator does not have SMP support
- enabled (see flag <seealso marker="#smp"><c>-smp</c></seealso>).</p>
</item>
<tag><marker id="+SDcpu"/><c><![CDATA[+SDcpu
DirtyCPUSchedulers:DirtyCPUSchedulersOnline]]></c></tag>
<item>
<p>Sets the number of dirty CPU scheduler threads to create and dirty
- CPU scheduler threads to set online when threading support has been
- enabled. The maximum for both values is 1024, and each value is
+ CPU scheduler threads to set online.
+ The maximum for both values is 1024, and each value is
further limited by the settings for normal schedulers:</p>
<list type="bulleted">
<item>The number of dirty CPU scheduler threads created cannot exceed
@@ -977,16 +959,14 @@
executing on ordinary schedulers. If the amount of dirty CPU
schedulers was allowed to be unlimited, dirty CPU bound jobs would
potentially starve normal jobs.</p>
- <p>This option is ignored if the emulator does not have threading
- support enabled.</p>
</item>
<tag><marker id="+SDPcpu"/><c><![CDATA[+SDPcpu
DirtyCPUSchedulersPercentage:DirtyCPUSchedulersOnlinePercentage]]></c></tag>
<item>
<p>Similar to <seealso marker="#+SDcpu"><c>+SDcpu</c></seealso> but
uses percentages to set the number of dirty CPU scheduler threads to
- create and the number of dirty CPU scheduler threads to set online
- when threading support has been enabled. Specified values must be
+ create and the number of dirty CPU scheduler threads to set online.
+ Specified values must be
&gt; 0. For example, <c>+SDPcpu 50:25</c> sets the number of dirty
CPU scheduler threads to 50% of the logical processors configured
and the number of dirty CPU scheduler threads online to 25% of the
@@ -1003,13 +983,11 @@
the combination of the options <c>+SDcpu 4:4 +SDPcpu 50:25</c> (in
either order) results in 2 dirty CPU scheduler threads (50% of 4) and
1 dirty CPU scheduler thread online (25% of 4).</p>
- <p>This option is ignored if the emulator does not have threading
- support enabled.</p>
</item>
<tag><marker id="+SDio"/><c><![CDATA[+SDio DirtyIOSchedulers]]></c></tag>
<item>
- <p>Sets the number of dirty I/O scheduler threads to create when
- threading support has been enabled. Valid range is 0-1024. By
+ <p>Sets the number of dirty I/O scheduler threads to create.
+ Valid range is 0-1024. By
default, the number of dirty I/O scheduler threads created is 10,
same as the default number of threads in the <seealso
marker="#async_thread_pool_size">async thread pool</seealso>.</p>
@@ -1019,8 +997,6 @@
expected to execute on dirty I/O schedulers. If the user should schedule CPU
bound jobs on dirty I/O schedulers, these jobs might starve ordinary
jobs executing on ordinary schedulers.</p>
- <p>This option is ignored if the emulator does not have threading
- support enabled.</p>
</item>
<tag><c><![CDATA[+sFlag Value]]></c></tag>
<item>
diff --git a/erts/doc/src/erl_dist_protocol.xml b/erts/doc/src/erl_dist_protocol.xml
index 610351db6c..a78b13aaa4 100644
--- a/erts/doc/src/erl_dist_protocol.xml
+++ b/erts/doc/src/erl_dist_protocol.xml
@@ -829,7 +829,31 @@ DiB == gen_digest(ChA, ICA)?
<item>
<p>The node understand UTF-8 encoded atoms.</p>
</item>
+ <tag><c>-define(DFLAG_MAP_TAG, 16#20000).</c></tag>
+ <item>
+ <p>The node understand the map tag.</p>
+ </item>
+ <tag><c>-define(DFLAG_BIG_CREATION, 16#40000).</c></tag>
+ <item>
+ <p>The node understand big node creation.</p>
+ </item>
+ <tag><c>-define(DFLAG_SEND_SENDER, 16#80000).</c></tag>
+ <item>
+ <p>
+ Use the <c>SEND_SENDER</c>
+ <seealso marker="#control_message">control message</seealso>
+ instead of the <c>SEND</c> control message and use the
+ <c>SEND_SENDER_TT</c> control message instead
+ of the <c>SEND_TT</c> control message.
+ </p>
+ </item>
</taglist>
+ <p>
+ There are also a collection of <c>DFLAG</c>s bitwise or:ed
+ together in the <c>DFLAGS_STRICT_ORDER_DELIVERY</c> macro.
+ These flags corresponds to features that require strict
+ ordering of data over distribution channels.
+ </p>
</section>
</section>
@@ -922,6 +946,7 @@ DiB == gen_digest(ChA, ICA)?
</item>
</taglist>
+ <marker id="control_message"/>
<p>The <c>ControlMessage</c> is a tuple, where the first element indicates
which distributed operation it encodes:</p>
@@ -1028,4 +1053,49 @@ DiB == gen_digest(ChA, ICA)?
</item>
</taglist>
</section>
+
+ <section>
+ <title>New Ctrlmessages for Erlang/OTP 21</title>
+ <taglist>
+ <tag><c>SEND_SENDER</c></tag>
+ <item>
+ <p><c>{22, FromPid, ToPid}</c></p>
+ <p>Followed by <c>Message</c>.</p>
+ <p>
+ This control messages replace the <c>SEND</c> control
+ message and will be sent when the distribution flag
+ <seealso marker="erl_dist_protocol#dflags"><c>DFLAG_SEND_SENDER</c></seealso>
+ has been negotiated in the connection setup handshake.
+ </p>
+ <note><p>
+ Messages encoded before the connection has
+ been set up may still use the <c>SEND</c> control
+ message. However, once a <c>SEND_SENDER</c> or <c>SEND_SENDER_TT</c>
+ control message has been sent, no more <c>SEND</c>
+ control messages will be sent in the same direction
+ on the connection.
+ </p></note>
+ </item>
+ <tag><c>SEND_SENDER_TT</c></tag>
+ <item>
+ <p><c>{23, FromPid, ToPid, TraceToken}</c></p>
+ <p>Followed by <c>Message</c>.</p>
+ <p>
+ This control messages replace the <c>SEND_TT</c> control
+ message and will be sent when the distribution flag
+ <seealso marker="erl_dist_protocol#dflags"><c>DFLAG_SEND_SENDER</c></seealso>
+ has been negotiated in the connection setup handshake.
+ </p>
+ <note><p>
+ Messages encoded before the connection has
+ been set up may still use the <c>SEND_TT</c> control
+ message. However, once a <c>SEND_SENDER</c> or <c>SEND_SENDER_TT</c>
+ control message has been sent, no more <c>SEND_TT</c>
+ control messages will be sent in the same direction
+ on the connection.
+ </p></note>
+ </item>
+ </taglist>
+ </section>
+
</chapter>
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index 5afac46d21..e6b983b6c2 100644
--- a/erts/doc/src/erlang.xml
+++ b/erts/doc/src/erlang.xml
@@ -189,6 +189,14 @@
</taglist>
</desc>
</datatype>
+
+ <datatype>
+ <name name="dist_handle"></name>
+ <desc>
+ <p>An opaque handle identifing a distribution channel.</p>
+ </desc>
+ </datatype>
+
</datatypes>
<funcs>
@@ -1223,6 +1231,141 @@ end</code>
</func>
<func>
+ <name name="dist_ctrl_get_data" arity="1"/>
+ <fsummary>Get distribution channel data to pass to another node.</fsummary>
+ <desc>
+ <p>
+ Get distribution channel data from the local node that is
+ to be passed to the remote node. The distribution channel
+ is identified by <c><anno>DHandle</anno></c>. If no data
+ is available, the atom <c>none</c> is returned. One
+ can request to be informed by a message when more
+ data is available by calling
+ <seealso marker="erlang#dist_ctrl_get_data_notification/1"><c>erlang:dist_ctrl_get_data_notification(DHandle)</c></seealso>.
+ </p>
+ <note><p>
+ Only the process registered as distribution
+ controller for the distribution channel identified by
+ <c><anno>DHandle</anno></c> is allowed to call this
+ function.
+ </p></note>
+ <p>
+ This function is used when implementing an alternative
+ distribution carrier using processes as distribution
+ controllers. <c><anno>DHandle</anno></c> is retrived
+ via the callback
+ <seealso marker="erts:alt_dist#hs_data_f_handshake_complete"><c>f_handshake_complete</c></seealso>.
+ More information can be found in the documentation of
+ <seealso marker="erts:alt_dist#distribution_module">ERTS
+ User's Guide ➜ How to implement an Alternative Carrier
+ for the Erlang Distribution ➜ Distribution Module</seealso>.
+ </p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="dist_ctrl_get_data_notification" arity="1"/>
+ <fsummary>Request notification about available outgoing distribution channel data.</fsummary>
+ <desc>
+ <p>
+ Request notification when more data is available to
+ fetch using
+ <seealso marker="erlang#dist_ctrl_get_data/1"><c>erlang:dist_ctrl_get_data(DHandle)</c></seealso>
+ for the distribution channel identified by
+ <c><anno>DHandle</anno></c>. When more data is present,
+ the caller will be sent the message <c>dist_data</c>.
+ Once a <c>dist_data</c> messages has been sent, no
+ more <c>dist_data</c> messages will be sent until
+ the <c>dist_ctrl_get_data_notification/1</c> function has been called
+ again.
+ </p>
+ <note><p>
+ Only the process registered as distribution
+ controller for the distribution channel identified by
+ <c><anno>DHandle</anno></c> is allowed to call this
+ function.
+ </p></note>
+ <p>
+ This function is used when implementing an alternative
+ distribution carrier using processes as distribution
+ controllers. <c><anno>DHandle</anno></c> is retrived
+ via the callback
+ <seealso marker="erts:alt_dist#hs_data_f_handshake_complete"><c>f_handshake_complete</c></seealso>.
+ More information can be found in the documentation of
+ <seealso marker="erts:alt_dist#distribution_module">ERTS
+ User's Guide ➜ How to implement an Alternative Carrier
+ for the Erlang Distribution ➜ Distribution Module</seealso>.
+ </p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="dist_ctrl_input_handler" arity="2"/>
+ <fsummary>Register distribution channel input handler process.</fsummary>
+ <desc>
+ <p>
+ Register an alternate input handler process for the
+ distribution channel identified by <c><anno>DHandle</anno></c>.
+ Once this function has been called, <c><anno>InputHandler</anno></c>
+ is the only process allowed to call
+ <seealso marker="erlang#dist_ctrl_put_data/2"><c>erlang:dist_ctrl_put_data(DHandle, Data)</c></seealso>
+ with the <c><anno>DHandle</anno></c> identifing this distribution
+ channel.
+ </p>
+ <note><p>
+ Only the process registered as distribution
+ controller for the distribution channel identified by
+ <c><anno>DHandle</anno></c> is allowed to call this
+ function.
+ </p></note>
+ <p>
+ This function is used when implementing an alternative
+ distribution carrier using processes as distribution
+ controllers. <c><anno>DHandle</anno></c> is retrived
+ via the callback
+ <seealso marker="erts:alt_dist#hs_data_f_handshake_complete"><c>f_handshake_complete</c></seealso>.
+ More information can be found in the documentation of
+ <seealso marker="erts:alt_dist#distribution_module">ERTS
+ User's Guide ➜ How to implement an Alternative Carrier
+ for the Erlang Distribution ➜ Distribution Module</seealso>.
+ </p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="dist_ctrl_put_data" arity="2"/>
+ <fsummary>Pass data into the VM from a distribution channel.</fsummary>
+ <desc>
+ <p>
+ Deliver distribution channel data from a remote node to the
+ local node.
+ </p>
+ <note><p>
+ Only the process registered as distribution
+ controller for the distribution channel identified by
+ <c><anno>DHandle</anno></c> is allowed to call this
+ function unless an alternate input handler process
+ has been registered using
+ <seealso marker="erlang#dist_ctrl_input_handler/2"><c>erlang:dist_ctrl_input_handler(DHandle, InputHandler)</c></seealso>.
+ If an alternate input handler has been registered, only
+ the registered input handler process is allowed to call
+ this function.
+ </p></note>
+ <p>
+ This function is used when implementing an alternative
+ distribution carrier using processes as distribution
+ controllers. <c><anno>DHandle</anno></c> is retrived
+ via the callback
+ <seealso marker="erts:alt_dist#hs_data_f_handshake_complete"><c>f_handshake_complete</c></seealso>.
+ More information can be found in the documentation of
+ <seealso marker="erts:alt_dist#distribution_module">ERTS
+ User's Guide ➜ How to implement an Alternative Carrier
+ for the Erlang Distribution ➜ Distribution Module</seealso>.
+ </p>
+ </desc>
+ </func>
+
+ <func>
<name name="element" arity="2"/>
<fsummary>Return the Nth element of a tuple.</fsummary>
<type_desc variable="N">1..tuple_size(<anno>Tuple</anno>)</type_desc>
@@ -4304,7 +4447,6 @@ RealSystem = system + MissedSystem</code>
<desc>
<p><c><anno>Locking</anno></c> is one of the following:</p>
<list type="bulleted">
- <item><c>false</c> (emulator without SMP support)</item>
<item><c>port_level</c> (port-specific locking)</item>
<item><c>driver_level</c> (driver-specific locking)</item>
</list>
@@ -4708,8 +4850,8 @@ RealSystem = system + MissedSystem</code>
selected for execution. Notice however that this does
<em>not</em> mean that no processes on priority <c>low</c>
or <c>normal</c> can run when processes
- are running on priority <c>high</c>. On the runtime
- system with SMP support, more processes can be running
+ are running on priority <c>high</c>. When using multiple
+ schedulers, more processes can be running
in parallel than processes on priority <c>high</c>. That is,
a <c>low</c> and a <c>high</c> priority process can
execute at the same time.</p>
@@ -4724,10 +4866,8 @@ RealSystem = system + MissedSystem</code>
execution.</p>
<note>
<p>Do not depend on the scheduling
- to remain exactly as it is today. Scheduling, at least on
- the runtime system with SMP support, is likely to be
- changed in a future release to use available
- processor cores better.</p>
+ to remain exactly as it is today. Scheduling is likely to be
+ changed in a future release to use available processor cores better.</p>
</note>
<p>There is <em>no</em> automatic mechanism for
avoiding priority inversion, such as priority inheritance
@@ -6239,8 +6379,7 @@ true</pre>
<p><c>statistics(exact_reductions)</c> is
a more expensive operation than
<seealso marker="#statistics_reductions">
- statistics(reductions)</seealso>,
- especially on an Erlang machine with SMP support.</p>
+ statistics(reductions)</seealso>.</p>
</note>
</desc>
</func>
@@ -6624,8 +6763,8 @@ ok
than available logical processors, this value may
be greater than <c>1.0</c>.</p>
<p>As of ERTS version 9.0, the Erlang runtime system
- with SMP support will as default have more schedulers
- than logical processors. This due to the dirty schedulers.</p>
+ will as default have more schedulers than logical processors.
+ This due to the dirty schedulers.</p>
<note>
<p><c>scheduler_wall_time</c> is by default disabled. To
enable it, use
@@ -7995,9 +8134,7 @@ ok
<taglist>
<tag><c>disabled</c></tag>
<item>
- <p>The emulator has only one scheduler thread. The
- emulator does not have SMP support, or have been
- started with only one scheduler thread.</p>
+ <p>The emulator has been started with only one scheduler thread.</p>
</item>
<tag><c>blocked</c></tag>
<item>
@@ -8360,8 +8497,7 @@ ok
</item>
<tag><c>smp_support</c></tag>
<item>
- <p>Returns <c>true</c> if the emulator has been compiled
- with SMP support, otherwise <c>false</c> is returned.</p>
+ <p>Returns <c>true</c>.</p>
</item>
<tag><marker id="system_info_start_time"/><c>start_time</c></tag>
<item>
@@ -8384,8 +8520,7 @@ ok
</item>
<tag><c>threads</c></tag>
<item>
- <p>Returns <c>true</c> if the emulator has been compiled
- with thread support, otherwise <c>false</c> is returned.</p>
+ <p>Returns <c>true</c>.</p>
</item>
<tag><c>thread_pool_size</c></tag>
<item>
@@ -10504,9 +10639,9 @@ true</pre>
<c>receive after 1 -> ok end</c>, except that <c>yield()</c>
is faster.</p>
<warning>
- <p>There is seldom or never any need to use this BIF,
- especially in the SMP emulator, as other processes have a
- chance to run in another scheduler thread anyway.
+ <p>There is seldom or never any need to use this BIF
+ as other processes have a chance to run in another scheduler
+ thread anyway.
Using this BIF without a thorough grasp of how the scheduler
works can cause performance degradation.</p>
</warning>
diff --git a/erts/doc/src/notes.xml b/erts/doc/src/notes.xml
index f6bc6e984b..050e84f0c1 100644
--- a/erts/doc/src/notes.xml
+++ b/erts/doc/src/notes.xml
@@ -603,7 +603,7 @@
marker="erts:erl"><c>erl</c></seealso> command.</p>
<p>
See <url
- href="http://pcre.org/original/changelog.txt"><c>http://pcre.org/original/changelog.txt</c></url>
+ href="http://pcre.org/original/changelog.txt">http://pcre.org/original/changelog.txt</url>
for information about changes made to PCRE between the
versions 8.33 and 8.40.</p>
<p>
@@ -3541,8 +3541,7 @@
<p>The previously introduced "eager check I/O" feature is
now enabled by default.</p>
<p>Eager check I/O can be disabled using the <c>erl</c>
- command line argument: <seealso
- marker="erl#+secio"><c>+secio false</c></seealso></p>
+ command line argument: <c>+secio false</c></p>
<p>Characteristics impact compared to previous
default:</p> <list> <item>Lower latency and smoother
management of externally triggered I/O operations.</item>
@@ -4323,8 +4322,7 @@
prioritized to the same extent as when eager check I/O is
disabled.</p>
<p>Eager check I/O can be enabled using the <c>erl</c>
- command line argument: <seealso
- marker="erl#+secio"><c>+secio true</c></seealso></p>
+ command line argument: <c>+secio true</c></p>
<p>Characteristics impact when enabled:</p> <list>
<item>Lower latency and smoother management of externally
triggered I/O operations.</item> <item>A slightly reduced