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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>
+ <item>
+ <p>
+ Fix fd leak when using async thread pool</p>
+ <p> When using the async thread pool, if an erlang
+ process asks to open a file and it gets shutdown/killed
+ while the file:open/2 call hasn't returned, it's possible
+ to leak a file descriptor against the target file. This
+ has now been fixed. (Thanks to Filipe David Manana)</p>
+ <p>
+ Own Id: OTP-10677</p>
+ </item>
+ <item>
+ <p>
+ Use sys/types.h instead of string.h to pull ssize_t
+ definition to erl_driver.h. This fixes build issue on
+ NetBSD. (Thanks to Yamamoto Takashi).</p>
+ <p>
+ Own Id: OTP-10699</p>
+ </item>
+ <item>
+ <p>
+ Arguments given with the -run or -s flags to erl are now
+ translated according to the file name encoding mode of
+ the runtime system.</p>
+ <p>
+ Own Id: OTP-10702</p>
+ </item>
+ <item>
+ <p>
+ The octet counters in the gen_tcp/inet interface could
+ behave in unexpected ways on 64bit platforms. The
+ behaviour is now as expected.</p>
+ <p>
+ Own Id: OTP-10746</p>
+ </item>
+ <item>
+ <p>
+ Certain linux kernels, most notably in redhat and CentOS
+ distribution, had a bug in writev which generated an
+ infinite loop in the tcp code of the VM. The bug is now
+ worked around.</p>
+ <p>
+ Own Id: OTP-10747</p>
+ </item>
+ <item>
+ <p>
+ A process that got killed (got an exit signal) while
+ operating on a compresseed file, could cause a
+ segmentation fault in the VM. This is now corrected.
+ Thanks to Filipe David Manana for identifying the problem
+ and submitting a solution.</p>
+ <p>
+ Own Id: OTP-10748</p>
+ </item>
+ <item>
+ <p>
+ Windows previously used three digit exponent in
+ formatting which caused difference between platforms, as
+ can be seen by float_to_list/1. This has now been fixed.</p>
+ <p>
+ Own Id: OTP-10751</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>Process optimizations. The most notable:</p> <list>
+ <item>New internal process table implementation allowing
+ for both parallel reads as well as writes. Especially
+ read operations have become really cheap. This reduce
+ contention in various situations. For example when,
+ spawning processes, terminating processes, sending
+ messages, etc.</item> <item>Optimizations of run queue
+ management reducing contention.</item>
+ <item>Optimizations of process state changes reducing
+ contention.</item> </list> <p>These changes imply changes
+ of the characteristics the system. Most notable: changed
+ timing in the system.</p>
+ <p>
+ Own Id: OTP-9892 Aux Id: OTP-10167 </p>
+ </item>
+ <item>
+ <p>
+ Non-blocking code loading. Earlier when an Erlang module
+ was loaded, all other execution in the VM were halted
+ while the load operation was carried out in single
+ threaded mode. Now modules are loaded without blocking
+ the VM. Processes may continue executing undisturbed in
+ parallel during the entire load operation. The load
+ operation is completed by making the loaded code visible
+ to all processes in a consistent way with one single
+ atomic instruction. Non-blocking code loading will
+ improve realtime characteristics when modules are
+ 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>Remove VxWorks support</p>
+ <p>
+ Own Id: OTP-10146</p>
+ </item>
+ <item>
+ <p>
+ Added a general framework for executing benchmarks of
+ Erlang/OTP. Benchmarks for the Erlang VM and mnesia have
+ been incorporated in the framework. </p>
+ <p>
+ For details about how to add more benchmarks see
+ $ERL_TOP/HOWTO/BENCHMARKS.md in the source distribution.</p>
+ <p>
+ Own Id: OTP-10156</p>
+ </item>
+ <item>
+ <p>
+ Optimized deletion of ETS-tables which significantly
+ improves performance when large amounts of temporary
+ tables are used.</p>
+ <p>
+ This change imply changes of the characteristics the
+ system. Most notable: changed timing in the system.</p>
+ <p>
+ Own Id: OTP-10167 Aux Id: OTP-9892 </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>
+ New internal header scheme for allocators</p>
+ <p>
+ Impact: Reduces size on object allocated in multiblock
+ carriers by one word</p>
+ <p>
+ Own Id: OTP-10273 Aux Id: kunagi-20 [20] </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.This reduce
+ contention in various situations. For example when,
+ creating ports, terminating ports, etc. </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> <item>Improving responsiveness by bumping
+ reductions for a process calling a driver callback
+ directly.</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> <tag>Reduction cost of calling driver
+ callbacks</tag> <item>Calling a driver callback is quite
+ costly. This was previously not reflected in reduction
+ cost at all. Since the reduction cost now has increased,
+ a process performing lots of direct driver calls will be
+ scheduled out more frequently than before.</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: OTP-9892 </p>
+ </item>
+ <item>
+ <p>
+ The experimental support for packages has been removed.</p>
+ <p>
+ Own Id: OTP-10348 Aux Id: kunagi-316 [227] </p>
+ </item>
+ <item>
+ <p>
+ Wrong parameters when setting seq_trace-tokens from
+ within a trace-pattern could crash the VM. This is now
+ corrected.</p>
+ <p>
+ Own Id: OTP-10522</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>
+ Add insert_element/3 and delete_element/2</p>
+ <p>
+ Own Id: OTP-10643</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-9892, OTP-10336 </p>
+ </item>
+ <item>
+ <p>
+ The previously (in R15) proposed scheduler wakeup
+ strategy is now used by default. This strategy is not as
+ quick to forget about previous overload as the previous
+ strategy.</p>
+ <p>
+ This change imply changes of the characteristics the
+ system. Most notable: When a small overload comes and
+ then disappears repeatedly, the system will for a bit
+ longer time be willing to wake up schedulers than before.
+ Timing in the system will due to this also change.</p>
+ <p>
+ The previous strategy can still be enabled by passing the
+ <seealso marker="erl#+sws">+sws legacy</seealso> command
+ line flag to <c>erl</c>.</p>
+ <p>
+ Own Id: OTP-10661 Aux Id: OTP-10033 </p>
+ </item>
+ <item>
+ <p>
+ The <seealso marker="#+stbt">+stbt</seealso> command line
+ argument of <c>erl</c> was added. This argument can be
+ used for trying to set scheduler bind type. Upon failure
+ unbound schedulers will be used.</p>
+ <p>
+ Own Id: OTP-10668</p>
+ </item>
+ <item>
+ <p>
+ Support ANSI in console</p>
+ <p>
+ Unix platforms will no longer filter control sequences to
+ the ttsl driver thus enabling ANSI and colors in console.
+ (Thanks to Pedram Nimreezi)</p>
+ <p>
+ Own Id: OTP-10678</p>
+ </item>
+ <item>
+ <p>Add file:allocate/3 operation</p>
+ <p>This operation allows pre-allocation of space for
+ files. It succeeds only on systems that support such
+ operation. (Thanks to Filipe David Manana)</p>
+ <p>
+ Own Id: OTP-10680</p>
+ </item>
+ <item>
+ <p>Treat <c>-Wreturn-type</c> warnings as error when
+ using GCC (Thanks to Tuncer Ayaz)</p>
+ <p>
+ Own Id: OTP-10683</p>
+ </item>
+ <item>
+ <p>
+ Implement ./otp_build configure --enable-silent-rules</p>
+ <p>
+ With silent rules, the output of make is less verbose and
+ compilation warnings are easier to spot. Silent rules are
+ disabled by default and can be disabled or enabled at
+ will by make V=0 and make V=1. (Thanks to Anthony Ramine)</p>
+ <p>
+ Own Id: OTP-10726</p>
+ </item>
+ <item>
+ <p>
+ Use share flags for all file operations on Windows.
+ Thanks to Filipe David Borba Manana.</p>
+ <p>
+ Own Id: OTP-10727</p>
+ </item>
+ <item>
+ <p>
+ Make/fakefop adjustments. Thanks to Tuncer Ayaz and
+ Sebastian Rasmussen.</p>
+ <p>
+ Own Id: OTP-10733</p>
+ </item>
+ <item>
+ <p>
+ The runtime system will now by default use 10 async
+ threads if thread support has been enabled when building
+ the runtime system.</p>
+ <p>
+ This will prevent long blocking file-operations from
+ blocking scheduler threads for long periods of time,
+ which can be harmful. Apart from file-operations, it also
+ effects other operations scheduled on the async thread
+ pool by user implemented drivers.</p>
+ <p>
+ The amount of async threads can be controlled by using
+ the <seealso
+ marker="erl#async_thread_pool_size"><c>+A</c></seealso>
+ command line argument of <c>erl(1)</c>. When running some
+ offline tools you <em>might</em> want to disable async
+ threads, but you are advised <em>not</em> to in the
+ general case. Instead, you might want to increase the
+ amount of async threads used.</p>
+ <p>
+ This change imply changes of the characteristics the
+ system compared to the previous default. The
+ responsiveness of the system as a whole will be improved.
+ Operations scheduled on the async thread pool will get an
+ increased latency. The throughput of these operations may
+ increase, or decrease depending on the type of the
+ operations and how they get scheduled. In the case of
+ file operations, the throughput very much depends on how
+ the Erlang application access files. Multiple concurrent
+ accesses to different files have the potential of an
+ increased throughput.</p>
+ <p>
+ Own Id: OTP-10736</p>
+ </item>
+ <item>
+ <p>
+ The default reader group limit has been increased to 64
+ from 8. This limit can be set using the <c>+rg</c>
+ command line argument of <c>erl(1)</c>.</p>
+ <p>
+ This change of default value will reduce lock contention
+ on ETS tables using the <c>read_concurrency</c> option at
+ the expense of memory consumption when the amount of
+ schedulers and logical processors are beween 8 and 64.
+ For more information, see documentation of the <c>+rg</c>
+ command line argument of <c>erl(1)</c>.</p>
+ <p>
+ Own Id: OTP-10737</p>
+ </item>
+ <item>
+ <p>
+ New BIF float_to_list/2 which solves a problem of
+ float_to_list/1 that doesn't allow specifying the number
+ of digits after the decimal point when formatting floats
+ (Thanks to Serge Aleynikov).</p>
+ <p>
+ Own Id: OTP-10752</p>
+ </item>
+ <item>
+ <p>
+ Limited support for unicode atoms in the external format
+ and in the internal representation of the vm. This is a
+ preparative feature in order to support communication
+ with future releases of Erlang/OTP that may create
+ unicode atoms.</p>
+ <p>
+ Own Id: OTP-10753</p>
+ </item>
+ <item>
+ <p>
+ Increased potential concurrency in ETS for
+ <c>write_concurrency</c> option. The number of internal
+ table locks has increased from 16 to 64. This makes it
+ four times less likely that two concurrent processes
+ writing to the same table would collide and thereby
+ serialized. The cost is an increased constant memory
+ footprint for tables using write_concurrency. The memory
+ consumption per inserted record is not affected. The
+ increased footprint can be particularly large if
+ <c>write_concurrency</c> is combined with
+ <c>read_concurrency</c>.</p>
+ <p>
+ Own Id: OTP-10787</p>
+ </item>
+ </list>
+ </section>
+
+</section>
+
<section><title>Erts 5.9.3.1</title>
<section><title>Known Bugs and Problems</title>