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<p>This document describes the changes made to the ERTS application.</p>
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<section><title>Erts 5.7.2</title>
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<section><title>Fixed Bugs and Malfunctions</title>
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Crash dumps should now cause less problems for the
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crashdump_viewer application. (For processes where arity
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was non-zero, the arguments are now longer printed - they
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used to be printed in a format that was not parseable.)</p>
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Own Id: OTP-7472 Aux Id: seq11019, 11292 </p>
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Processes could potentially get stuck on an offline
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<c>binary_to_atom/2</c> and
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<c>binary_to_existing_atom/2</c> could leak memory if
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they caused a <c>badarg</c> exception.</p>
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A process could under very rare circumstances erroneously
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Load balancing between schedulers could under rare
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circumstances cause an emulator crash.</p>
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<c>erlang:memory(processes_used)</c> always returned
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<c>0</c> instead of the correct value. (Thanks to Geoff
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<section><title>Improvements and New Features</title>
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Major improvements of the Erlang distribution for Erlang
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runtime systems with SMP support. Previously distribution
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port locks were heavily contended, and all encoding and
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decoding for a specific distribution channel had to be
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done in sequence. Lock contention due to the distribution
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is now negligible and both encoding and decoding of
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Erlang messages can be done in parallel.</p>
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The old atom cache protocol used by the Erlang
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distribution has been dropped since it effectively
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prevented all parallel encoding and decoding of messages
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passed over the same distribution channel.</p>
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A new atom cache protocol has been introduced which
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isolates atom cache accesses and makes parallel encoding
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and decoding of messages passed over the same
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distribution channel possible. The new atom cache
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protocol also use an atom cache size 8 times larger than
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before. The new atom cache protocol is documented in the
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ERTS users guide.</p>
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Erlang messages received via the distribution are now
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decoded by the receiving Erlang processes without holding
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any distribution channel specific locks. Erlang messages
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and signals sent over the distribution are as before
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encoded by the sending Erlang process, but now without
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holding any distribution channel specific locks during
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the encoding. That is, both encoding and decoding can be
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and are done in parallel regardless of distribution
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The part that cannot be parallelized is the atom cache
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updates. Atom cache updates are therefore now scheduled
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on the distribution port. Since it is only one entity per
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distribution channel doing this work there is no lock
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contention due to the atom cache updates.</p>
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The new runtime system does not understand the old atom
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cache protocol. New and old runtime systems can however
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still communicate, but no atom cache will be used.</p>
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Fixed a bug that caused error logging from
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<c>driver_select</c> sometimes with additional symptoms
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such as failing IP communications or even an emulator
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Own Id: OTP-7898 Aux Id: seq11304 </p>
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Improved SMP concurrency for ETS tables. Several mutating
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operations can now be performed truly concurrent on
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different records of the same table. To support this, the
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table has to be created with option
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<c>write_concurrency</c>, as it is achieved at the
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expense of some execution and memory overhead.
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<c>ets:select</c> and <c>select_count</c> has also been
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improved for all tables to not aquire exclusive table
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lock during the iteration.</p>
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erl (that is erl.exe and dyn_erl) and erlexec has been
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made more dynamic so no hard coded paths needs to added
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at installation time to erl (that is erl.ini and erl).
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Reltool will make use of this in a future release.</p>
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Added functionality to get higher resolution timestamp
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from system. The erlang:now function returns a timestamp
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that's not always consistent with the actual operating
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system time (due to resilience against large time changes
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in the operating system). The function os:timestamp/0 is
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added to get a similar timestamp as the one being
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returned by erlang:now, but untouched by Erlangs time
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correcting and smoothing algorithms. The timestamp
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returned by os:timestamp is always consistent with the
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operating systems view of time, like the calendar
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functions for getting wall clock time, but with higher
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resolution. Example of usage can be found in the os
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Two new options are added to open_port - spawn_executable
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which runs external executables in a controlled way, and
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spawn_driver which only opens port to loaded Erlang
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drivers. See the erlang manual page for details.</p>
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New functionality in ETS to transfer the ownership of a
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table. A table can either change owner be declaring an
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"heir", another process that will inherit the table if
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the owner terminates. A table can also change owner by
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calling a new function <c>ets:give_away</c>.</p>
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Updates to Tilera build environment.</p>
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A stack trace was unnecessarily saved during process
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User defined CPU topology and scheduler bind type can now
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be set from the command line when starting an emulator.
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For more information see the documentation of the
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<c>+sct</c>, and the <c>+sbt</c> emulator flags in the
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<c>erl(1)</c> documentation.</p>
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The CPU topologies returned from
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<c>erlang:system_info/1</c> and
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<c>erlang:system_flag/2</c> now always contain the
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<c>processor</c> level, also when not strictly necessary.</p>
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Various fixes in ETS: <c>ets:first</c> could return a
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deleted key in a fixated table. <c>ets:lookup</c> could
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return objects out of order if a deleted object was
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re-inserted into a fixed bag. <c>ets:delete_object</c>
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could fail to delete duplicate objects in a
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246
<section><title>Erts 5.7.1</title>
34
248
<section><title>Fixed Bugs and Malfunctions</title>
added
removed
erts/doc/src/notes.xml
