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Improve accuracy of timeouts using a premature timeout then
return to sleep with a shorter timeout just before requested
timeout. This approach is only used on certain platforms where
we know it improves the accuracy of the timeouts, e.g. MacOS X.
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* henrik/update-copyrightyear:
update copyright-year
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Lots of pthread platforms unnecessarily falled back on the pipe/select
solution. This since we tried to use the same monotonic clock source
for pthread_cond_timedwait() as used by OS monotonic time. This has
been fixed on most platforms by using another clock source.
Darwin can however not use pthread_cond_timedwait() with monotonic
clock source and has to use the pipe/select solution. On darwin we
now use select with _DARWIN_UNLIMITED_SELECT in order to be able to
handle a large amount of file descriptors.
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The atomic memory operations interface used the 'long' type and assumed that
it was of the same size as 'void *'. This is true on most platforms, however,
not on Windows 64.
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Large parts of the ethread library have been rewritten. The
ethread library is an Erlang runtime system internal, portable
thread library used by the runtime system itself.
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
`{read_concurrency, true}' option upon table creation. See the
documentation of `ets:new/2' for more information.
The ethread library can now also use the libatomic_ops library
for atomic memory accesses. This makes it possible for the
Erlang runtime system to utilize optimized atomic operations
on more platforms than before. Use the
`--with-libatomic_ops=PATH' configure command line argument
when specifying where the libatomic_ops installation is
located. The libatomic_ops library can be downloaded from:
http://www.hpl.hp.com/research/linux/atomic_ops/
The changed API of the ethread 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 ethread library.
Note: When building for x86, the ethread 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
`--enable-ethread-pre-pentium4-compatibility' configure command
line argument when configuring the system.
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