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<p>This document describes the changes made to the ERTS application.</p>
-<section><title>Erts 8.0</title>
-
- <section><title>Fixed Bugs and Malfunctions</title>
- <list>
- <item>
- <p>The handling of <c>on_load</c> functions has been
- improved. The major improvement is that if a code upgrade
- fails because the <c>on_load</c> function fails, the
- previous version of the module will now be retained.</p>
- <p>
- Own Id: OTP-12593</p>
- </item>
- <item>
- <p><c>is_builtin(erlang, apply, 3)</c> will now return
- <c>true</c>.</p>
- <p>
- Own Id: OTP-13034</p>
- </item>
- <item>
- <p>
- Fix <c>enif_get_list_length</c> to return false if list
- is improper or have length larger than <c>UINT_MAX</c>
- (did return true and an incorrect length value).</p>
- <p>
- Own Id: OTP-13288 Aux Id: PR913 </p>
- </item>
- <item>
- <p>
- Cleanup hipe signal handling code for x86 and make it
- more portable.</p>
- <p>
- Own Id: OTP-13341 Aux Id: PR951 </p>
- </item>
- <item>
- <p>
- Use fsync instead of fdatasync on Mac OSX.</p>
- <p>
- Own Id: OTP-13411</p>
- </item>
- <item>
- <p>
- Make sure to create a crash dump when running out of
- memory. This was accidentally removed in the erts-7.3
- release.</p>
- <p>
- Own Id: OTP-13419</p>
- </item>
- <item>
- <p>
- A bug has been fixed where if erlang was started +B on a
- unix platform it would be killed by a SIGUSR2 signal when
- creating a crash dump.</p>
- <p>
- Own Id: OTP-13425</p>
- </item>
- <item>
- <p>
- Fix race between <c>process_flag(trap_exit,true)</c> and
- a received exit signal.</p>
- <p>
- A process could terminate due to exit signal even though
- <c>process_flag(trap_exit,true)</c> had returned. A very
- specific timing between call to <c>process_flag/2</c> and
- exit signal from another scheduler was required for this
- to happen.</p>
- <p>
- Own Id: OTP-13452</p>
- </item>
- <item>
- <p>Don't search for non-existing Map keys twice</p>
- <p>For <c>maps:get/2,3</c> and <c>maps:find/2</c>,
- searching for an immediate key, e.g. an atom, in a small
- map, the search was performed twice if the key did not
- exist.</p>
- <p>
- Own Id: OTP-13459</p>
- </item>
- <item>
- <p>
- When a abnormally large distribution message is about to
- be sent, the VM has been changed to create a crash dump
- instead of a core dump.</p>
- <p>
- Own Id: OTP-13474</p>
- </item>
- <item>
- <p>
- Fix <c>erlang:process_info/2</c> type specification</p>
- <p>
- Own Id: OTP-13485 Aux Id: ERL-123 </p>
- </item>
- <item>
- <p>
- Fix bug in <c>open_port/2</c> with option <c>{args,
- List}</c>. A vm crash could be caused by an improper
- <c>List</c>.</p>
- <p>
- Own Id: OTP-13489 Aux Id: ERL-127 </p>
- </item>
- <item>
- <p>
- Don't crash on terminating processes with
- <c>erlang:system_profile/1,2</c></p>
- <p>
- Own Id: OTP-13494 Aux Id: ERL-126 </p>
- </item>
- <item>
- <p>
- Fixed bugs where the reduction counter was not handled
- correct.</p>
- <p>
- Own Id: OTP-13512</p>
- </item>
- <item>
- <p>
- Fixed typo in description of the <c>EPMD_DUMP_REQ</c>
- response.</p>
- <p>
- Own Id: OTP-13517</p>
- </item>
- <item>
- <p>
- Fixed a bug where a process flagged as sensitive would
- sometimes record its save_calls when it shouldn't.</p>
- <p>
- Own Id: OTP-13540</p>
- </item>
- <item>
- <p>
- Update configure scripts to not use hardcoded path for
- /bin/pwd and /bin/rm.</p>
- <p>
- Own Id: OTP-13562</p>
- </item>
- <item>
- <p>
- When passing a larger binary than the outputv callback of
- a linked-in driver can handle in one io vector slot, the
- binary is now split into multiple slots in the io vector.
- This change only effects system where the max size of an
- io vector slot is smaller then the word size of the
- system (e.g. Windows).</p>
- <p>
- This change means that it is now possible on Windows to
- send binaries that are larger than 4GB to port_comnmand,
- which is what is used for file:write, gen_tcp:send etc.</p>
- <p>
- Own Id: OTP-13628</p>
- </item>
- </list>
- </section>
-
-
- <section><title>Improvements and New Features</title>
- <list>
- <item>
- <p>
- The tracing support has been extended to allow a <seealso
- marker="erl_tracer">tracer module</seealso> to be the
- trace event handler instead of a process or port. The
- <seealso marker="erl_tracer">tracer module</seealso>
- makes it possible for trace tools to filter or manipulate
- trace event data without the trace event first haing to
- be copied from the traced process or port.</p>
- <p>
- With the introduction of this feature,
- <c>erlang:trace(all|existing, _, _)</c> now also returns
- the tracer process as part of the number of processes on
- which tracing is enabled. The is incompatible with the
- previous releases.</p>
- <p>
- *** POTENTIAL INCOMPATIBILITY ***</p>
- <p>
- Own Id: OTP-10267</p>
- </item>
- <item>
- <p>
- Introduce LTTng tracing of Erlang Runtime System</p>
- <p>
- For LTTng to be enabled OTP needs to be built with
- configure option <c>--with-dynamic-trace=lttng</c>.</p>
- <p>
- This feature introduces tracepoints for schedulers,
- drivers, memory carriers, memory and async thread pool.</p>
- <p> For a list of all tracepoints, see <seealso
- marker="runtime_tools:LTTng">Runtime Tools User's
- Guide</seealso> .</p>
- <p>
- Own Id: OTP-10282</p>
- </item>
- <item>
- <p>
- Add microstate accounting</p>
- <p>
- Microstate accounting is a way to track which state the
- different threads within ERTS are in. The main usage area
- is to pin point performance bottlenecks by checking which
- states the threads are in and then from there figuring
- out why and where to optimize.</p>
- <p>
- Since checking whether microstate accounting is on or off
- is relatively expensive only a few of the states are
- enabled by default and more states can be enabled through
- configure.</p>
- <p>
- There is a convinence module called msacc that has been
- added to runtime_tools that can assist in gathering and
- interpreting the data from Microstate accounting.</p>
- <p>
- For more information see <seealso
- marker="erts:erlang#statistics_microstate_accounting">erlang:statistics(microstate_accounting,
- _)</seealso> and the <seealso
- marker="runtime_tools:msacc">msacc</seealso> module in
- runtime_tools.</p>
- <p>
- Own Id: OTP-12345</p>
- </item>
- <item>
- <p>
- The port of Erlang/OTP to the realtime operating system
- OSE has been removed.</p>
- <p>
- Own Id: OTP-12573</p>
- </item>
- <item>
- <p>
- Sharing preserved copy for messages and exit signals</p>
- <p>
- Enable sharing preserved copy with configure option
- <c>--enable-sharing-preserving</c>. This will preserve
- sharing, within the process, when communication with
- other processes in the Erlang node. There is a trade-off,
- the copy is more costly but this cost can be reclaimed if
- there is a lot of sharing in the message. With this
- feature enabled literals will not be copied in a send
- except during a purge phase of the module where the
- literals are located. This feature is considered
- experimental in 19.0.</p>
- <p>
- Own Id: OTP-12590 Aux Id: OTP-10251 </p>
- </item>
- <item>
- <p>
- Halfword BEAM has been removed.</p>
- <p>
- Own Id: OTP-12883</p>
- </item>
- <item>
- <p>
- Added <seealso
- marker="kernel:os#perf_counter/1">os:perf_counter/1</seealso>.</p>
- <p>
- The perf_counter is a very very cheap and high resolution
- timer that can be used to timestamp system events. It
- does not have monoticity guarantees, but should on most
- OS's expose a monotonous time.</p>
- <p>
- Own Id: OTP-12908</p>
- </item>
- <item>
- <p>
- Support for a fragmented young heap generation. That is,
- the young heap generation can consist of multiple non
- continuous memory areas. The main reason for this change
- is to avoid extra copying of messages that could not be
- allocated directly on the receivers heap.</p>
- <p>
- Own Id: OTP-13047</p>
- </item>
- <item>
- <p>
- Erlang linked-in driver can now force the call to
- open_port to block until a call to erl_drv_init_ack is
- made inside the driver. This is useful when you want to
- do some asynchronous initialization, for example getting
- configuration from a pipe, and you want the initial
- open_port call to fail if the configuration is incomplete
- or wrong. See the erl_driver documentation for more
- details on the API.</p>
- <p>
- Own Id: OTP-13086</p>
- </item>
- <item>
- <p>
- Erlang linked-in drivers can now set their own pid's as
- seen in <c>erlang:port_info/1</c> by using the
- <c>erl_drv_set_pid</c> function. For more details see the
- erl_driver documentation.</p>
- <p>
- Own Id: OTP-13087</p>
- </item>
- <item>
- <p>
- The functionality behind <c>erlang:open_port/2</c> when
- called with spawn or spawn_executable has been redone so
- that the forking of the new program is done in a separate
- process called erl_child_setup. This allows for a much
- more robust implementation that uses less memory and does
- not block the entire emulator if the program to be
- started is on an un-accessible NFS. Benchmarks have shown
- this approach to be about 3-5 times as fast as the old
- approach where the fork/vfork was done by erts. This is a
- pure stability and performance fix, however some error
- messages may have changed, which is why it is marked as a
- backwards incompatible change.</p>
- <p>
- *** POTENTIAL INCOMPATIBILITY ***</p>
- <p>
- Own Id: OTP-13088</p>
- </item>
- <item>
- <p>Improved yielding strategy in the implementation of
- the following native functions:</p> <list>
- <item><c>erlang:binary_to_list/1</c></item>
- <item><c>erlang:binary_to_list/3</c></item>
- <item><c>erlang:bitstring_to_list/1</c></item>
- <item><c>erlang:list_to_binary/1</c></item>
- <item><c>erlang:iolist_to_binary/1</c></item>
- <item><c>erlang:list_to_bitstring/1</c></item>
- <item><c>binary:list_to_bin/1</c></item> </list> <p>This
- in order to improve performance of these functions.</p>
- <p>
- Own Id: OTP-13096</p>
- </item>
- <item>
- <p>
- All garbage collections of processes now bump reductions.
- Also the amount of reductions bumped when garbage
- collecting has been adjusted. It now better corresponds
- to the amount of work performed. This in order to improve
- the real time characteristics of the system.</p>
- <p>
- Own Id: OTP-13097</p>
- </item>
- <item>
- <p>New functions that can load multiple functions at once
- have been added to the '<c>code</c>' module. The
- functions are <c>code:atomic_load/1</c>,
- <c>code:prepare_loading/1</c>,
- <c>code:finish_loading/1</c>, and
- <c>code:ensure_modules_loaded/1</c>.</p>
- <p>
- Own Id: OTP-13111</p>
- </item>
- <item>
- <p>The <c>-boot_var</c> option for <c>erl</c> now only
- supports a single key and single value (as documented).
- The option used to allow multiple key/value pairs, but
- that behavior was undocumented.</p>
- <p>The function <c>erl_prim_loader:start/3</c> has been
- removed. Its documentation has also been removed.</p>
- <p>The undocumented and unsupported function
- <c>erl_prim_loader:get_files/2</c> has been removed.</p>
- <p>
- Own Id: OTP-13112</p>
- </item>
- <item>
- <p>
- Low level BIF <c>erlang:purge_module/1</c> is made more
- robust against incorrect use. Lingering processes that
- still refer the old code are now killed before the module
- is purged to prevent fatal VM behavior.</p>
- <p>
- Own Id: OTP-13122</p>
- </item>
- <item>
- <p>
- Improved dirty scheduler implementation. For more
- information see the <seealso
- marker="erl_nif#dirty_nifs">NIF documentation</seealso>.</p>
- <p>
- Note that support for determining whether dirty NIF
- support exist or not at compile time using the C
- preprocessor macro <c>ERL_NIF_DIRTY_SCHEDULER_SUPPORT</c>
- has been removed.</p>
- <p>
- Own Id: OTP-13123</p>
- </item>
- <item>
- <p>
- Various optimizations done to process dictionary access.</p>
- <p>
- Own Id: OTP-13167</p>
- </item>
- <item>
- <p>
- Added max_heap_size process flag. See erlang:process_flag
- for more details.</p>
- <p>
- Own Id: OTP-13174</p>
- </item>
- <item>
- <p>
- Allow dynamic drivers and NIF libraries to be built with
- gcc option <c>-fvisibility=hidden</c> for faster loading
- and more optimized code.</p>
- <p>
- Own Id: OTP-13227</p>
- </item>
- <item>
- <p>
- Add <c>erlang:process_info(Pid,
- garbage_collection_info)</c> which returns extended
- garbage_collection information. For more details see the
- documentation.</p>
- <p>
- Own Id: OTP-13265</p>
- </item>
- <item>
- <p>
- The functions <c>erlang:list_to_integer/1</c> and
- <c>string:to_integer/1</c> have been optimized for large
- inputs.</p>
- <p>
- Own Id: OTP-13293</p>
- </item>
- <item>
- <p>
- Improved memory allocation strategy for hipe native code
- on x86_64 (amd64) architectures by reserving enough low
- virtual address space needed for the HiPE/AMD64 small
- code model. The default virtual address area for hipe
- code is set to 512Mb, but can be changed with emulator
- flag <c>+MXscs</c>.</p>
- <p>
- Own Id: OTP-13359</p>
- </item>
- <item>
- <p>
- Introduction of configurable management of data referred
- to by the message queue of a process. Each process can be
- configured individually.</p>
- <p>
- It is now possible to configure the message queue of a
- process, so that all data referred by it will be kept
- outside of the heap, and by this prevent this data from
- being part of garbage collections.</p>
- <p>
- For more information see the documentation of <seealso
- marker="erlang#process_flag_message_queue_data"><c>process_flag(message_queue_data,
- MQD)</c></seealso>.</p>
- <p>
- Own Id: OTP-13366 Aux Id: OTP-13047 </p>
- </item>
- <item>
- <p>
- Processes now yield when scanning large message queues
- and not finding a matching message. This in order to
- improve real time characteristics.</p>
- <p>
- Own Id: OTP-13401</p>
- </item>
- <item>
- <p>
- Optimized an erts internal function that is used to
- traverse erlang terms. The internal function was mainly
- used by term_to_binary and comparison of terms.
- Benchmarks have shown up to a 10% performance increase in
- those functions after the optimization.</p>
- <p>
- Own Id: OTP-13440</p>
- </item>
- <item>
- <p>
- Add the following NIF API functions:</p>
- <p>
- <list> <item><seealso
- marker="erl_nif#enif_cpu_time"><c>enif_cpu_time</c></seealso></item>
- <item><seealso
- marker="erl_nif#enif_now_time"><c>enif_now_time</c></seealso></item>
- <item><seealso
- marker="erl_nif#enif_make_unique_integer"><c>enif_make_unique_integer</c></seealso></item>
- <item><seealso
- marker="erl_nif#enif_is_process_alive"><c>enif_is_process_alive</c></seealso></item>
- <item><seealso
- marker="erl_nif#enif_is_port_alive"><c>enif_is_port_alive</c></seealso></item>
- <item><seealso
- marker="erl_nif#enif_term_to_binary"><c>enif_term_to_binary</c></seealso></item>
- <item><seealso
- marker="erl_nif#enif_binary_to_term"><c>enif_binary_to_term</c></seealso></item>
- <item><seealso
- marker="erl_nif#enif_port_command"><c>enif_port_command</c></seealso></item>
- </list></p>
- <p>
- for details of what each function does, see the erl_nif
- documentation.</p>
- <p>
- Own Id: OTP-13442</p>
- </item>
- <item>
- <p>
- Optimize <c>'++'</c> operator and <c>lists:append/2</c>
- by using a single pass to build a new list while checking
- for properness.</p>
- <p>
- Own Id: OTP-13487</p>
- </item>
- <item>
- <p>
- Handle terms (pids,ports and refs) from nodes with a
- 'creation' value larger than 3. This is a preparation of
- the distribution protocol to allow OTP 19 nodes to
- correctly communicate with future nodes (20 or higher).
- The 'creation' value differentiates different
- incarnations of the same node (name).</p>
- <p>
- Own Id: OTP-13488</p>
- </item>
- <item>
- <p>
- Don't send unasked for systemd notifications in epmd</p>
- <p>
- Own Id: OTP-13493 Aux Id: PR-999 </p>
- </item>
- <item>
- <p>
- The enif_send API has been extended to allow NULL to be
- used as the message environment. When used this way, a
- message environent is implicitly created and the given
- term is copied into that environment before sending. This
- can be an optimization if many small messages are being
- sent by the nif.</p>
- <p>
- Own Id: OTP-13495</p>
- </item>
- <item>
- <p>
- The tracing support has been extended to allow tracing on
- ports. Ports can be traced on using the 'ports', 'send'
- and 'receive' trace flags.</p>
- <p>
- The first argument of <seealso
- marker="erts:erlang#trace/3">erlang:trace/3</seealso> has
- been extended so that <c>'all'</c>, <c>'existing'</c> and
- <c>'new'</c> now include both processes and ports. New
- <c>Tracee</c> variants, <c>'all_processes'</c>,
- <c>'all_ports'</c>, <c>'existing_processes'</c> etc have
- been added to specify only processes or ports.</p>
- <p>
- *** POTENTIAL INCOMPATIBILITY ***</p>
- <p>
- Own Id: OTP-13496</p>
- </item>
- <item>
- <p>
- When the <c>'procs'</c> trace flag is enabled, a
- <c>'spawned'</c> trace event is now also generated by a
- newly created process. The previous event <c>'spawn'</c>
- remains, but as it is generated by the process that did
- the spawn, it is not guaranteed that it is ordered with
- other trace events from the newly spawned process. So
- when tracking the lifetime of a process this new event
- should be used as the creation event.</p>
- <p>
- This new trace event is marked as an incompatabiliy
- because tools that expect certain trace events when
- enabling 'procs' will have to updated.</p>
- <p>
- *** POTENTIAL INCOMPATIBILITY ***</p>
- <p>
- Own Id: OTP-13497</p>
- </item>
- <item>
- <p>
- Add the <seealso
- marker="erts:erlang#match_spec_test/3">erlang:match_spec_test/3</seealso>
- function. The functions allows the testing of match
- specifications for both tracing and ets tables. It can be
- used to test that a match specification does the expected
- filtering on specific data. It also returns more verbose
- error reasons for incorrectly constructed match
- specifications.</p>
- <p>
- Own Id: OTP-13501</p>
- </item>
- <item>
- <p>
- The erts internal tracing support has been changed to
- have much less overhead and be more scalable.</p>
- <p>
- This rewrite does not break any backwards
- incompatabilities, but it does change the ordering of
- some trace messages when compared to previous releases.
- It should be noted that this only applies to trace
- messages sent to processes or ports, it does not apply to
- the new tracer module. However in future releases they
- may also be effected by this.</p>
- <p>
- Trace messages are only guaranteed to be ordered from one
- traced process or port. In previous releases this was not
- visible as a <c>'send'</c> trace message would always
- arrive before the corresponding <c>'receive'</c> trace
- message that is no longer always the case. This also
- means that timestamped trace messages may seem to arrive
- out of order as the timestamp is taken when the event is
- triggered and not when it is put in the queue of the
- tracer.</p>
- <p>
- Own Id: OTP-13503</p>
- </item>
- <item>
- <p>
- Add possibility to filter <c>send</c> and <c>receive</c>
- trace with match specifications.</p>
- <p>
- Own Id: OTP-13507</p>
- </item>
- <item>
- <p>
- Add <c>maps:update_with/3,4</c> and <c>maps:take/2</c></p>
- <p>
- Own Id: OTP-13522 Aux Id: PR-1025 </p>
- </item>
- <item>
- <p>
- Introduce LTTng tracing via Erlang tracing.</p>
- <p>
- For LTTng to be enabled OTP needs to be built with
- configure option <c>--with-dynamic-trace=lttng</c>.</p>
- <p>The dynamic trace module <c>dyntrace</c> is now
- capable to be used as a LTTng sink for Erlang tracing.
- For a list of all tracepoints, see <seealso
- marker="runtime_tools:LTTng">Runtime Tools User's
- Guide</seealso> .</p>
- <p>This feature also introduces an incompatible change in
- trace tags. The trace tags <c>gc_start</c> and
- <c>gc_end</c> has been split into <c>gc_minor_start</c>,
- <c>gc_minor_end</c> and <c>gc_major_start</c>,
- <c>gc_major_end</c>.</p>
- <p>
- *** POTENTIAL INCOMPATIBILITY ***</p>
- <p>
- Own Id: OTP-13532</p>
- </item>
- <item>
- <p>
- Print heap pointers for garbing processes during
- crashdump</p>
- <p>
- Own Id: OTP-13541 Aux Id: PR-1026 </p>
- </item>
- <item>
- <p>
- Changed and improved low level memory statistics returned
- by <c>erlang:system_info/1</c>. The info for
- <c>erts_mmap</c> has been moved from <c>mseg_alloc</c> to
- its own section returned by <c>{allocator,
- erts_mmap}</c>.</p>
- <p>
- Own Id: OTP-13560</p>
- </item>
- <item>
- <p>
- Add enif_snprintf to the NIF API</p>
- <p>
- The fucntion <c>enif_snprintf</c> is similar to
- <c>snprintf</c> call but can handle formating of Erlang
- terms via <c>%T</c> format specifier.</p>
- <p>
- Own Id: OTP-13580</p>
- </item>
- <item>
- <p>The warning in the documentation for
- <c>erlang:raise/3</c> has been removed. It is now
- officially perfectly fine to use raise/3 in production
- code. (Thanks to Per Hedeland.)</p>
- <p>
- Own Id: OTP-13599</p>
- </item>
- <item>
- <p>
- Add <c>-start_epmd</c> command line option, this lets you
- disable automatic starting of epmd when starting a
- distributed node.</p>
- <p>
- Add <c>-epmd_module</c> command line option, this lets
- you specify a module to register and lookup node names
- in. The default module is <c>erl_epmd</c>.</p>
- <p>
- Own Id: OTP-13627</p>
- </item>
- <item>
- <p>
- <c>erlang:halt</c> now truncates strings longer than 200
- characters instead of failing with <c>badarg</c>.</p>
- <p>
- Own Id: OTP-13630</p>
- </item>
- </list>
- </section>
-
-</section>
-
<section><title>Erts 7.3.1</title>
<section><title>Fixed Bugs and Malfunctions</title>