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authorErlang/OTP <[email protected]>2015-05-12 18:18:55 +0200
committerErlang/OTP <[email protected]>2015-05-12 18:18:55 +0200
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</header>
<p>This document describes the changes made to the ERTS application.</p>
+<section><title>Erts 7.0</title>
+
+ <section><title>Fixed Bugs and Malfunctions</title>
+ <list>
+ <item>
+ <p>
+ Fix issuing with spaces and quoting in the arguments when
+ using erlang:open_port spawn_executable on windows. The
+ behavior now mimics how unix works. This change implies a
+ backwards incompatibility for how spawn_executable works
+ on windows.</p>
+ <p>
+ *** POTENTIAL INCOMPATIBILITY ***</p>
+ <p>
+ Own Id: OTP-11905</p>
+ </item>
+ <item>
+ <p>
+ Fix global call trace when hipe compiled code call beam
+ compiled functions. Tracing of beam functions should now
+ alway work regardless who the caller is.</p>
+ <p>
+ Own Id: OTP-11939</p>
+ </item>
+ <item>
+ <p>
+ Correct cache alignment for ETS <c>write_concurrency</c>
+ locks to improve performance by reduced false sharing.
+ May increase memory footprint for tables with
+ <c>write_concurrency</c>.</p>
+ <p>
+ Own Id: OTP-11974</p>
+ </item>
+ <item>
+ <p>
+ All possibly blocking operations in the fd/spawn and
+ terminal driver have been converted to non-blocking
+ operations. Before this fix it was possible for the VM to
+ be blocked for a long time if the entity consuming
+ stdout/stderr did not consume it fast enough.</p>
+ <p>
+ Own Id: OTP-12239</p>
+ </item>
+ <item>
+ <p>
+ Add missing overhead for offheap binaries created from
+ external format. This fix can improve the garbage
+ collection of large binaries originating from
+ <c>binary_to_term</c> or messages from remote nodes.</p>
+ <p>
+ Own Id: OTP-12554</p>
+ </item>
+ <item>
+ <p>
+ Ensure hashing of zero is consistent</p>
+ <p> Erlang treats positive and negative zero as
+ equal:</p>
+ <p>
+ <c>true = 0.0 =:= 0.0/-1</c></p>
+ <p>However, Erlangs hash functions: hash, phash and
+ phash2 did not reflect this behaviour. The hash values
+ produced by the different hash functions would not be
+ identical for positive and negative zero.</p> <p>This
+ change ensures that hash value of positive zero is always
+ produced regardless of the signedness of the zero float,
+ i.e.,</p>
+ <p>
+ <c>true = erlang:phash2(0.0) =:=
+ erlang:phash2(0.0/-1)</c></p>
+ <p>
+ Own Id: OTP-12641</p>
+ </item>
+ <item>
+ <p>
+ Ensure NIF term creation disallows illegal floating point
+ values and too long atoms. Such values will cause a NIF
+ to throw badarg exception when it returns.</p>
+ <p>
+ Own Id: OTP-12655</p>
+ </item>
+ <item>
+ <p>
+ Fixed building of Map results from match_specs</p>
+ <p>
+ A faulty "box-value" entered into the heap which could
+ cause a segmentation fault in the garbage collector if it
+ was written on a heap fragment.</p>
+ <p>
+ Own Id: OTP-12656</p>
+ </item>
+ <item>
+ <p>
+ Fix hipe bug when matching a "writable" binary. The bug
+ has been seen to sometimes cause a failed binary matching
+ of a correct utf8 character, but other symptoms are also
+ possible.</p>
+ <p>
+ Own Id: OTP-12667</p>
+ </item>
+ <item>
+ <p>
+ Keep dirty schedulers from waking other schedulers.</p>
+ <p>
+ Own Id: OTP-12685</p>
+ </item>
+ <item>
+ <p>
+ Disable floating point exceptions if the VM is compiled
+ by clang/llvm. This is a known long-standing problem in
+ clang/llvm.</p>
+ <p>
+ Own Id: OTP-12717</p>
+ </item>
+ <item>
+ <p>
+ Fix bug in <c>file:sendfile</c> for FreeBSD causing not
+ the entire file to be sent.</p>
+ <p>
+ Own Id: OTP-12720</p>
+ </item>
+ </list>
+ </section>
+
+
+ <section><title>Improvements and New Features</title>
+ <list>
+ <item>
+ <p>
+ Add <c>md5</c> and <c>module</c> entries to
+ <c>?MODULE:module_info/0/1</c> and remove obsolete entry
+ 'import'.</p>
+ <p>
+ *** POTENTIAL INCOMPATIBILITY ***</p>
+ <p>
+ Own Id: OTP-11940</p>
+ </item>
+ <item>
+ <p>
+ Debug function <c>erlang:display/1</c> shows content of
+ binaries and bitstrings, not only the length.</p>
+ <p>
+ Own Id: OTP-11941</p>
+ </item>
+ <item>
+ <p>The time functionality of Erlang has been extended.
+ This both includes a <seealso
+ marker="time_correction#The_New_Time_API">new
+ API</seealso> for time, as well as <seealso
+ marker="time_correction#Time_Warp_Modes">time warp
+ modes</seealso> which alters the behavior of the system
+ when system time changes. <em>You are strongly encouraged
+ to use the new API</em> instead of the old API based on
+ <seealso
+ marker="erlang#now/0"><c>erlang:now/0</c></seealso>.
+ <c>erlang:now/0</c> has been deprecated since it is and
+ forever will be a scalability bottleneck. For more
+ information see the <seealso
+ marker="time_correction">Time and Time
+ Correction</seealso> chapter of the ERTS User's
+ Guide.</p>
+ <p>Besides the API changes and time warp modes a lot of
+ scalability and performance improvements regarding time
+ management has been made internally in the runtime
+ system. Examples of such improvements are scheduler
+ specific timer wheels, scheduler specific BIF timer
+ management, parallel retrieval of monotonic time and
+ system time on systems with primitives that are not
+ buggy.</p>
+ <p>
+ Own Id: OTP-11997</p>
+ </item>
+ <item>
+ <p><c>erlang:function_exported(M, F, A)</c> will now
+ return <c>true</c> if <c>M:F/A</c> refers to a BIF.</p>
+ <p>
+ *** POTENTIAL INCOMPATIBILITY ***</p>
+ <p>
+ Own Id: OTP-12099</p>
+ </item>
+ <item>
+ <p>
+ New BIF: <c>erlang:get_keys/0</c>, lists all keys
+ associated with the process dictionary. Note:
+ <c>erlang:get_keys/0</c> is auto-imported.</p>
+ <p>
+ *** POTENTIAL INCOMPATIBILITY ***</p>
+ <p>
+ Own Id: OTP-12151 Aux Id: seq12521 </p>
+ </item>
+ <item>
+ <p>
+ Make distributed send of large messages yield to improve
+ real-time characteristics.</p>
+ <p>
+ Own Id: OTP-12232</p>
+ </item>
+ <item>
+ <p>
+ Use high accuracy poll timeouts</p>
+ <p>
+ Where available, use poll/select API's that can handle
+ time resolutions less than 1ms. In the cases where such
+ API's are not available the timeout is rounded up to the
+ nearest ms.</p>
+ <p>
+ Own Id: OTP-12236</p>
+ </item>
+ <item>
+ <p>
+ The internal group to user_drv protocol has been changed
+ to be synchronous in order to guarantee that output sent
+ to a process implementing the user_drv protocol is
+ printed before replying. This protocol is used by the
+ standard_output device and the ssh application when
+ acting as a client. </p>
+ <p>
+ This change changes the previous unlimited buffer when
+ printing to standard_io and other devices that end up in
+ user_drv to 1KB.</p>
+ <p>
+ *** POTENTIAL INCOMPATIBILITY ***</p>
+ <p>
+ Own Id: OTP-12240</p>
+ </item>
+ <item>
+ <p>The previously introduced "eager check I/O" feature is
+ now enabled by default.</p>
+ <p>Eager check I/O can be disabled using the <c>erl</c>
+ command line argument: <seealso
+ marker="erl#+secio"><c>+secio false</c></seealso></p>
+ <p>Characteristics impact compared to previous
+ default:</p> <list> <item>Lower latency and smoother
+ management of externally triggered I/O operations.</item>
+ <item>A slightly reduced priority of externally triggered
+ I/O operations.</item> </list>
+ <p>
+ Own Id: OTP-12254 Aux Id: OTP-12117 </p>
+ </item>
+ <item>
+ <p>
+ Properly support maps in match_specs</p>
+ <p>
+ Own Id: OTP-12270</p>
+ </item>
+ <item>
+ <p>
+ The notice that a crashdump has been written has been
+ moved to be printed before the crashdump is generated
+ instead of afterwords. The wording of the notice has also
+ been changed.</p>
+ <p>
+ *** POTENTIAL INCOMPATIBILITY ***</p>
+ <p>
+ Own Id: OTP-12292</p>
+ </item>
+ <item>
+ <p>
+ New function <c>ets:take/2</c>. Works the same as
+ <c>ets:delete/2</c> but also returns the deleted
+ object(s).</p>
+ <p>
+ Own Id: OTP-12309</p>
+ </item>
+ <item>
+ <p>
+ Tracing with cpu_timestamp option has been enabled on
+ Linux.</p>
+ <p>
+ Own Id: OTP-12366</p>
+ </item>
+ <item>
+ <p>
+ ets:info/1,2 now contains information about whether
+ write_concurrency or read_concurrency is enabled.</p>
+ <p>
+ Own Id: OTP-12376</p>
+ </item>
+ <item>
+ <p>
+ Improved usage of <c>gcc</c>'s builtins for atomic memory
+ access. These are used when no other implementation of
+ atomic memory operations is available. For example, when
+ compiling for ARM when <c>libatomic_ops</c> is not
+ available.</p>
+ <p>
+ The largest improvement will be seen when compiling with
+ a <c>gcc</c> with support for the <c>__atomic_*</c>
+ builtins (using a <c>gcc</c> of at least version 4.7),
+ but also when only the legacy <c>__sync_*</c> builtins
+ are available (using a <c>gcc</c> of at least version
+ 4.1) an improvement can be seen.</p>
+ <p>
+ For more information see the "<seealso
+ marker="doc/installation_guide:INSTALL#Advanced-configuration-and-build-of-ErlangOTP_Configuring_Atomic-Memory-Operations-and-the-VM">Atomic
+ Memory Operations and the VM</seealso>" section of
+ <c>$ERL_TOP/HOWTO/INSTALL.md</c>.</p>
+ <p>
+ Own Id: OTP-12383</p>
+ </item>
+ <item>
+ <p>
+ Introduce <c>math:log2/1</c> function to math module.</p>
+ <p>
+ Own Id: OTP-12411</p>
+ </item>
+ <item>
+ <p>
+ Remove perfctr support</p>
+ <p>
+ Development of perfctr in the linux kernel ceased in
+ 2010. The perfctr support code in the Erlang VM is thus
+ effectively dead code and therefor removed.</p>
+ <p>
+ Own Id: OTP-12508</p>
+ </item>
+ <item>
+ <p><c>zlib:inflateChunk/2</c> has been added. It works
+ like <c>zlib:inflate/2</c>, but decompresses no more data
+ than will fit in the buffer configured by
+ <c>zlib:setBufSize/2</c>.</p>
+ <p>
+ Own Id: OTP-12548</p>
+ </item>
+ <item>
+ <p>
+ Use linear search for small select_val arrays</p>
+ <p>
+ Own Id: OTP-12555</p>
+ </item>
+ <item>
+ <p>
+ New BIF ets:update_counter/4 with a default object as
+ argument, which will be inserted in the table if the key
+ was not found.</p>
+ <p>
+ Own Id: OTP-12563</p>
+ </item>
+ <item>
+ <p>
+ Export missing types from zlib module</p>
+ <p>
+ Own Id: OTP-12584</p>
+ </item>
+ <item>
+ <p>
+ Use persistent hashmaps for large Maps <p>Maps will use a
+ persistent hashmap implementation when the number of
+ pairs in a Map becomes sufficiently large. The change
+ will occur when a Map reaches 33 pairs in size but this
+ limit might change in the future.</p></p>
+ <p>The most significant impact for the user by this
+ change is speed, and to a lesser degree memory
+ consumption and introspection of Maps. Memory consumption
+ size is probalistic but lesser than <c>gb_trees</c> or
+ <c>dict</c> for instance. Any other impacts will be
+ transparent for the user except for the following
+ changes.</p>
+ <p>Semantics of Maps have changed in two incompatible
+ ways compared to the experimental implementation in OTP
+ 17:</p> <list> <item>Hashing of maps is done different by
+ <c>erlang:phash2/1,2</c>, <c>erlang:phash/1</c> and
+ <c>erlang:hash/2</c>.</item> <item>Comparing two maps
+ with ==, /=, =&lt;, &lt;, &gt;= and &gt;, is done
+ different if the keys contain floating point
+ numbers.</item> </list>
+ <p>
+ *** POTENTIAL INCOMPATIBILITY ***</p>
+ <p>
+ Own Id: OTP-12585</p>
+ </item>
+ <item>
+ <p>
+ Scalability improvement for <seealso
+ marker="erlang#make_ref/0">erlang:make_ref/0</seealso>,
+ and other functionality that create references. Each
+ scheduler now manage its own set of references. By this
+ no communication at all is needed when creating
+ references.</p>
+ <p>
+ Previous implementation generated a strictly
+ monotonically increasing sequence of references
+ corresponding to creation time on the runtime system
+ instance. This is <em>not</em> the case with current
+ implementation. You can only expect reference to be
+ unique. The Erlang/OTP documentation has never mentioned
+ anything else but the uniqueness property, so this change
+ <em>is</em> fully compatible. The only reason we've
+ marked this as a potential incompatibility is since an
+ early draft for an Erlang specification mentions strict
+ monotonicity as a property.</p>
+ <p>
+ If you need to create data with a strict monotonicity
+ property use <seealso
+ marker="erlang#unique_integer/1">erlang:unique_integer([monotonic])</seealso>.
+ Do <em>not</em> use the deprecated <seealso
+ marker="erlang:now/0">erlang:now()</seealso>.</p>
+ <p>
+ *** POTENTIAL INCOMPATIBILITY ***</p>
+ <p>
+ Own Id: OTP-12610</p>
+ </item>
+ <item>
+ <p>
+ Enable different abort signal from heart</p>
+ <p>By using environment variable HEART_KILL_SIGNAL, heart
+ can now use a different signal to kill the old running
+ Erlang.</p>
+ <p>By default the signal is SIGKILL but SIGABRT may also
+ be used by setting environment variable:
+ HEART_KILL_SIGNAL=SIGABRT</p>
+ <p>
+ Own Id: OTP-12613 Aux Id: seq12826 </p>
+ </item>
+ <item>
+ <p>
+ Update autconf to latest version 2015-03-04</p>
+ <p>
+ Own Id: OTP-12646</p>
+ </item>
+ <item>
+ <p>
+ Optimization of timers internally in the VM. This include
+ process timers (<c>receive ... after</c>), port timers
+ (<c>driver_set_timer()</c>) as well as BIF timers
+ (<c>erlang:send_after()</c>/<c>erlang:start_timer()</c>).</p>
+ <p>
+ Each scheduler thread now has its own lock-free timer
+ service instead of one locked central service. This
+ dramatically improves performance of timer management on
+ systems with a large amount of schedulers and timers.</p>
+ <p>
+ The timer service internal data structure has also been
+ optimized to be able to handle more timers than before.
+ That is, each timer service is by its self able to handle
+ more timers without dramatic performance loss than the
+ old centralized timer service.</p>
+ <p>
+ The API of BIF timers has also been extended. Timeout
+ values are for example no longer limited to 32-bit
+ integers. For more information see the documentation of
+ <seealso
+ marker="erlang#start_timer/4"><c>erlang:start_timer/4</c></seealso>,
+ <seealso
+ marker="erlang#send_after/4"><c>erlang:send_after/4</c></seealso>,
+ <seealso
+ marker="erlang#cancel_timer/2"><c>erlang:cancel_timer/2</c></seealso>,
+ and <seealso
+ marker="erlang#read_timer/2"><c>erlang:read_timer/2</c></seealso>.</p>
+ <p>
+ Own Id: OTP-12650 Aux Id: OTP-11997 </p>
+ </item>
+ <item>
+ <p>
+ Specialize instructions from common assembler patterns</p>
+ <p>Specialize common instructions of <c>rem</c>,
+ <c>band</c>, <c>minus</c> and <c>plus</c> in the beam
+ loader. This will reduce the number of fetches and thus
+ lessen the instruction dispatch pressure during runtime
+ and speed up those operations in some common cases.</p>
+ <p>Specialize move patterns from x-registers to the stack
+ with a new <c>move_window</c> instruction. This change
+ will reduce instruction dispatch pressure.</p>
+ <p>
+ Own Id: OTP-12690</p>
+ </item>
+ <item>
+ <p>
+ Fix cross compilation for Android.</p>
+ <p>
+ Own Id: OTP-12693</p>
+ </item>
+ <item>
+ <p>
+ Fix incorrect use of autoconf macro AC_EGREP_CPP, which
+ could cause faulty configuration if run from a path
+ containing the string 'yes'.</p>
+ <p>
+ Own Id: OTP-12706</p>
+ </item>
+ <item>
+ <p>
+ Minimal Java version is now 1.6</p>
+ <p>
+ Own Id: OTP-12718</p>
+ </item>
+ <item>
+ <p>
+ Send format and args on process exit to error_logger</p>
+ <p>
+ Previously, the emulator would generate a whole string
+ with values and call the error_logger passing
+ <c>"~s~n"</c>. This changes it to a format string
+ containing <c>~p</c> with the respective values as
+ arguments.</p>
+ <p>
+ Own Id: OTP-12735</p>
+ </item>
+ </list>
+ </section>
+
+</section>
+
<section><title>Erts 6.4.1</title>
<section><title>Fixed Bugs and Malfunctions</title>