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authorFredrik Gustafsson <fredrik@erlang.org>2013-01-17 16:50:33 +0100
committerFredrik Gustafsson <fredrik@erlang.org>2013-01-17 16:50:33 +0100
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</header>
<p>This document describes the changes made to the ERTS application.</p>
+<section><title>Erts 5.10</title>
+
+ <section><title>Fixed Bugs and Malfunctions</title>
+ <list>
+ <item>
+ <p>
+ Set new peeled off SCTP socket to nonblocking socket
+ (Thanks to Jonas Falkevik)</p>
+ <p>
+ Own Id: OTP-10491</p>
+ </item>
+ <item>
+ <p>
+ Fix various typos (thanks to Tuncer Ayaz)</p>
+ <p>
+ Own Id: OTP-10611</p>
+ </item>
+ </list>
+ </section>
+
+
+ <section><title>Improvements and New Features</title>
+ <list>
+ <item>
+ <p>
+ A boolean socket option 'ipv6_v6only' for IPv6 sockets
+ has been added. The default value of the option is OS
+ dependent, so applications aiming to be portable should
+ consider using <c>{ipv6_v6only,true}</c> when creating an
+ <c>inet6</c> listening/destination socket, and if
+ neccesary also create an <c>inet</c> socket on the same
+ port for IPv4 traffic. See the documentation.</p>
+ <p>
+ Own Id: OTP-8928 Aux Id: kunagi-193 [104] </p>
+ </item>
+ <item>
+ <p>It is now allowed to define stubs for BIFs, to allow
+ type specs to be written for BIFs. For example, if there
+ is BIF called <c>lists:member/2</c>, a dummy definition
+ of <c>lists:member/2</c> is now allowed.</p>
+ <p>
+ Own Id: OTP-9861</p>
+ </item>
+ <item>
+ <p>
+ Code loading and upgrade are now done without blocking
+ the emulator in single threaded mode. This will improve
+ realtime characteristics when code is loaded/upgraded on
+ a running SMP system.</p>
+ <p>
+ Own Id: OTP-9974</p>
+ </item>
+ <item>
+ <p>In the SMP emulator, turning on and off tracing will
+ no longer take down the system to single-scheduling. </p>
+ <p>
+ Own Id: OTP-10122</p>
+ </item>
+ <item>
+ <p>
+ Tuple funs (deprecated in R15B) are no longer supported.</p>
+ <p>
+ *** POTENTIAL INCOMPATIBILITY ***</p>
+ <p>
+ Own Id: OTP-10170</p>
+ </item>
+ <item>
+ <p>Major port improvements. The most notable:</p> <list>
+ <item>New internal port table implementation allowing for
+ both parallel reads as well as writes. Especially read
+ operations have become really cheap.</item> <item>Dynamic
+ allocation of port structures. This allow for a much
+ larger maximum amount of ports allowed as a default. The
+ previous default of 1024 has been raised to 65536.
+ Maximum amount of ports can be set using the <seealso
+ marker="erts:erl#+Q">+Q</seealso> command line flag of
+ <seealso marker="erts:erl">erl(1)</seealso>. The
+ previously used environment variable <c>ERL_MAX_PORTS</c>
+ has been deprecated and scheduled for removal in
+ OTP-R17.</item> <item>Major rewrite of scheduling of port
+ tasks. Major benefits of the rewrite are reduced
+ contention on run queue locks, and reduced amount of
+ memory allocation operations needed. The rewrite was also
+ necessary in order to make it possible to schedule
+ signals from processes to ports.</item> <item>Improved
+ internal thread progress functionality for easy
+ management of unmanaged threads. This improvement was
+ necessary for the rewrite of the port task
+ scheduling.</item> <item>Rewrite of all process to port
+ signal implementations in order to make it possible to
+ schedule those operations. All port operations can now be
+ scheduled which allows for reduced lock contention on the
+ port lock as well as truly asynchronous communication
+ with ports.</item> <item>Optimized lookup of port handles
+ from drivers.</item> <item>Optimized driver lookup when
+ creating ports.</item> <item>Preemptable <seealso
+ marker="erts:erlang#ports-0">erlang:ports/0</seealso>
+ BIF.</item> </list>
+ <p>These changes imply changes of the characteristics of
+ the system. The most notable:</p> <taglist> <tag>Order of
+ signal delivery.</tag> <item>The previous implementation
+ of the VM has delivered signals from processes to ports
+ in a synchronous stricter fashion than required by the
+ language. As of ERTS version 5.10, signals are truly
+ asynchronously delivered. The order of signal delivery
+ still adheres to the requirements of the language, but
+ only to the requirements. That is, some signal sequences
+ that previously always were delivered in one specific
+ order may now from time to time be delivered in different
+ orders. This may cause Erlang programs that have made
+ <em>false assumptions</em> about signal delivery order to
+ fail even though they previously succeeded. For more
+ information about signal ordering guarantees, see the
+ chapter on <seealso
+ marker="erts:communication">communication</seealso> in
+ the ERTS user's guide. The <seealso
+ marker="erts:erl#+n">+n</seealso> command line flag of
+ <seealso marker="erts:erl">erl(1)</seealso> can be
+ helpful when trying to find signaling order bugs in
+ Erlang code that have been exposed by these
+ changes.</item> <tag>Latency of signals sent from
+ processes to ports.</tag> <item>Signals from processes to
+ ports where previously always delivered immediately. This
+ kept latency for such communication to a minimum, but it
+ could cause lock contention which was very expensive for
+ the system as a whole. In order to keep this latency low
+ also in the future, most signals from processes to ports
+ are by default still delivered immediately as long as no
+ conflicts occur. Such conflicts include not being able to
+ acquire the port lock, but also include other conflicts.
+ When a conflict occur, the signal will be scheduled for
+ delivery at a later time. A scheduled signal delivery may
+ cause a higher latency for this specific communication,
+ but improves the overall performance of the system since
+ it reduce lock contention between schedulers. The default
+ behavior of only scheduling delivery of these signals on
+ conflict can be changed by passing the <seealso
+ marker="erts:erl#+spp">+spp</seealso> command line flag
+ to <seealso marker="erts:erl">erl(1)</seealso>. The
+ behavior can also be changed on port basis using the
+ <seealso
+ marker="erts:erlang#open_port_parallelism">parallelism</seealso>
+ option of the <seealso
+ marker="erts:erlang#open_port-2">open_port/2</seealso>
+ BIF.</item> <tag>Execution time of the
+ <c>erlang:ports/0</c> BIF.</tag> <item>Since <seealso
+ marker="erts:erlang#ports-0">erlang:ports/0</seealso> now
+ can be preempted, the responsiveness of the system as a
+ whole has been improved. A call to <c>erlang:ports/0</c>
+ may, however, take a much longer time to complete than
+ before. How much longer time heavily depends on the
+ system load.</item> </taglist>
+ <p><em>Potential incompatibilities</em>:</p> <list>
+ <item><c>driver_send_term()</c> has been deprecated and
+ has been scheduled for removal in OTP-R17. Replace usage
+ of <c>driver_send_term()</c> with usage of <seealso
+ marker="erts:erl_driver#erl_drv_send_term">erl_drv_send_term()</seealso>.</item>
+ <item><c>driver_output_term()</c> has been deprecated and
+ has been scheduled for removal in OTP-R17. Replace usage
+ of <c>driver_output_term()</c> with usage of <seealso
+ marker="erts:erl_driver#erl_drv_output_term">erl_drv_output_term()</seealso>.</item>
+ <item>The new function <seealso
+ marker="erts:erl_driver#erl_drv_busy_msgq_limits">erl_drv_busy_msgq_limits()</seealso>
+ has been added in order to able to control management of
+ port queues.</item> </list>
+ <p>The <seealso
+ marker="erts:erl_driver#version_management">driver API
+ version</seealso> has been bumped to 2.1 from 2.0 due to
+ the above changes in the driver API.</p>
+ <p>
+ *** POTENTIAL INCOMPATIBILITY ***</p>
+ <p>
+ Own Id: OTP-10336 Aux Id: kunagi-138
+ [b5b97f67-fe34-46dc-93e6-a2931576db12] </p>
+ </item>
+ <item>
+ <p>
+ Erlang specification 4.7.3 defines max tuple size to
+ 65535 elements It is now enforced to no more than
+ 16777215 elements (arity 24 bits)</p>
+ <p>
+ Previous edge cases (28 bits) were not validated and
+ could cause undefined behaviour.</p>
+ <p>
+ *** POTENTIAL INCOMPATIBILITY ***</p>
+ <p>
+ Own Id: OTP-10633</p>
+ </item>
+ <item>
+ <p>
+ The previous default of a maximum of 32768 simultaneous
+ processes has been raised to 262144. This value can be
+ changed using the the <seealso
+ marker="erl#+P">+P</seealso> command line flag of
+ <seealso marker="erl">erl(1)</seealso>. Note that the
+ value passed now is considered as a hint, and that actual
+ value chosen in most cases will be a power of two.</p>
+ <p>
+ *** POTENTIAL INCOMPATIBILITY ***</p>
+ <p>
+ Own Id: OTP-10647 Aux Id: OTP-10336 </p>
+ </item>
+ </list>
+ </section>
+
+</section>
+
<section><title>Erts 5.9.3.1</title>
<section><title>Known Bugs and Problems</title>