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diff --git a/lib/stdlib/doc/src/notes.xml b/lib/stdlib/doc/src/notes.xml index 23d1e8b7de..6c618bc798 100644 --- a/lib/stdlib/doc/src/notes.xml +++ b/lib/stdlib/doc/src/notes.xml @@ -30,6 +30,142 @@ </header> <p>This document describes the changes made to the STDLIB application.</p> +<section><title>STDLIB 1.17.1</title> + + <section><title>Fixed Bugs and Malfunctions</title> + <list> + <item> + <p>reference() has been substituted for ref() in the + documentation.</p> + <p> + Own Id: OTP-8733</p> + </item> + </list> + </section> + + + <section><title>Improvements and New Features</title> + <list> + <item> + <p> + The ms_transform now warns if the fun head shadows + surrounding variables (just like the warnings you would + get for an ordinary fun in the same context).</p> + <p> + Own Id: OTP-6759</p> + </item> + <item> + <p> + ets:select_reverse/{1,2,3} are now documented.</p> + <p> + Own Id: OTP-7863</p> + </item> + <item> + <p> + Large parts of the <c>ethread</c> library have been + rewritten. The <c>ethread</c> library is an Erlang + runtime system internal, portable thread library used by + the runtime system itself.</p> + <p> + Most notable improvement is a reader optimized rwlock + implementation which dramatically improve the performance + of read-lock/read-unlock operations on multi processor + systems by avoiding ping-ponging of the rwlock cache + lines. The reader optimized rwlock implementation is used + by miscellaneous rwlocks in the runtime system that are + known to be read-locked frequently, and can be enabled on + ETS tables by passing the <seealso + marker="stdlib:ets#new_2_read_concurrency">{read_concurrency, + true}</seealso> option upon table creation. See the + documentation of <seealso + marker="stdlib:ets#new/2">ets:new/2</seealso> for more + information. The reader optimized rwlock implementation + can be fine tuned when starting the runtime system. For + more information, see the documentation of the <seealso + marker="erts:erl#+rg">+rg</seealso> command line argument + of <c>erl</c>.</p> + <p> + There is also a new implementation of rwlocks that is not + optimized for readers. Both implementations interleaves + readers and writers during contention as opposed to, + e.g., the NPTL (Linux) pthread rwlock implementation + which use either a reader or writer preferred strategy. + The reader/writer preferred strategy is problematic since + it starves threads doing the non-preferred operation.</p> + <p> + The new rwlock implementations in general performs better + in ERTS than common pthread implementations. However, in + some extremely heavily contended cases this is not the + case. Such heavy contention can more or less only appear + on ETS tables. This when multiple processes do very large + amounts of write locked operations simultaneously on the + same table. Such use of ETS is bad regardless of rwlock + implementation, will never scale, and is something we + strongly advise against.</p> + <p> + The new rwlock implementations depend on atomic + operations. If no native atomic implementation is found, + a fallback solution will be used. Using the fallback + implies a performance degradation. That is, it is more + important now than before to build OTP with a native + atomic implementation.</p> + <p> + The <c>ethread</c> library contains native atomic + implementations for, x86 (32 and 64 bit), powerpc (32 + bit), sparc V9 (32 and 64 bit), and tilera (32 bit). On + other hardware gcc's builtin support for atomic memory + access will be used if such exists. If no such support is + found, <c>configure</c> will warn about no atomic + implementation available.</p> + <p> + The <c>ethread</c> library can now also use the + <c>libatomic_ops</c> library for atomic memory accesses. + This makes it possible for the Erlang runtime system to + utilize optimized native atomic operations on more + platforms than before. If <c>configure</c> warns about no + atomic implementation available, try using the + <c>libatomic_ops</c> library. Use the <seealso + marker="doc/installation_guide:INSTALL#How-to-Build-and-Install-ErlangOTP_A-Closer-Look-at-the-individual-Steps_Configuring">--with-libatomic_ops=PATH</seealso> + <c>configure</c> command line argument when specifying + where the <c>libatomic_ops</c> installation is located. + The <c>libatomic_ops</c> library can be downloaded from: + <url + href="http://www.hpl.hp.com/research/linux/atomic_ops/">http://www.hpl.hp.com/research/linux/atomic_ops/</url></p> + <p> + The changed API of the <c>ethread</c> library has also + caused modifications in the Erlang runtime system. + Preparations for the to come "delayed deallocation" + feature has also been done since it depends on the + <c>ethread</c> library.</p> + <p> + <em>Note</em>: When building for x86, the <c>ethread</c> + library will now use instructions that first appeared on + the pentium 4 processor. If you want the runtime system + to be compatible with older processors (back to 486) you + need to pass the <seealso + marker="doc/installation_guide:INSTALL#How-to-Build-and-Install-ErlangOTP_A-Closer-Look-at-the-individual-Steps_Configuring">--enable-ethread-pre-pentium4-compatibility</seealso> + <c>configure</c> command line argument when configuring + the system.</p> + <p> + Own Id: OTP-8544</p> + </item> + <item> + <p> + Some Built In Functions (BIFs) from the module erlang was + never made autoimported for backward compatibility + reasons. As local functions now override autoimports, new + autoimports is no longer a problem, why the following + BIFs are finally made autoimported: monitor/2, monitor/3, + demonitor/2, demonitor/3, error/1, error/2, + integer_to_list/2, list_to_integer/2.</p> + <p> + Own Id: OTP-8763</p> + </item> + </list> + </section> + +</section> + <section><title>STDLIB 1.17</title> <section><title>Fixed Bugs and Malfunctions</title> |