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diff --git a/erts/doc/src/notes.xml b/erts/doc/src/notes.xml index 7501ccd9ce..3c3129d543 100644 --- a/erts/doc/src/notes.xml +++ b/erts/doc/src/notes.xml @@ -32,6 +32,742 @@ <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> + Make file:datasync 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 an 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> + Fixed a race-condition bug where the emulator could crash + when <c>erlang:system_profile/1,2</c> was enabled and a + process had to be re-scheduled during termination.</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 hard-coded 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_command, + which is what is used for file:write, gen_tcp:send etc.</p> + <p> + Own Id: OTP-13628</p> + </item> + <item> + <p> + Workaround of Maps output in crashdumps. Currently the + atom 'undefined' is generated instead of Map data if a + Map type is encountered during crash.</p> + <p> + Own Id: OTP-13657</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 having 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> + Make it possible to monitor/demonitor ports using the + <seealso + marker="erlang#monitor/2">erlang:monitor/2</seealso> API. + The process and port information functions have also been + updated to include information about monitors from + processes to ports.</p> + <p> + Own Id: OTP-11384</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 convenience 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 real-time 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. In addition + 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 pids 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 modules 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> <note><list> <item><p>The + dirty scheduler support is still + <em>experimental</em>.</p></item> <item><p>The 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></item> <item><p>The + <c>enif_is_on_dirty_scheduler()</c> function has been + removed. Use <seealso + marker="erl_nif#enif_thread_type"><c>enif_thread_type()</c></seealso> + instead.</p></item> </list></note> + <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. max_heap_size allows + the user to limit the maximum heap used by a process. See + <seealso + marker="erlang#process_flag/2">erlang:process_flag</seealso> + 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 environment 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 incompatibility + 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 + incompatibilities, 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 function <c>enif_snprintf</c> is similar to + <c>snprintf</c> call but can handle formatting 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.</p> + <p> + Own Id: OTP-13599</p> + </item> + <item> + <p> + Fix bugs caused by the VM sometimes truncating object + sizes or offsets to 32 bits on 64-bit hosts. These bugs + were mainly found when working with large unicode strings + and nifs environments.</p> + <p> + Own Id: OTP-13606</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 look-up 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> + <item> + <p> + Fix possible race in poller wake up on windows</p> + <p> + Own Id: OTP-13634</p> + </item> + </list> + </section> + +</section> + <section><title>Erts 7.3.1</title> <section><title>Fixed Bugs and Malfunctions</title> |