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Andres Freund b64d92f1a5 Add a basic atomic ops API abstracting away platform/architecture details. ... Several upcoming performance/scalability improvements require atomic operations. This new API avoids the need to splatter compiler and architecture dependent code over all the locations employing atomic ops. For several of the potential usages it'd be problematic to maintain both, a atomics using implementation and one using spinlocks or similar. In all likelihood one of the implementations would not get tested regularly under concurrency. To avoid that scenario the new API provides a automatic fallback of atomic operations to spinlocks. All properties of atomic operations are maintained. This fallback - obviously - isn't as fast as just using atomic ops, but it's not bad either. For one of the future users the atomics ontop spinlocks implementation was actually slightly faster than the old purely spinlock using implementation. That's important because it reduces the fear of regressing older platforms when improving the scalability for new ones. The API, loosely modeled after the C11 atomics support, currently provides 'atomic flags' and 32 bit unsigned integers. If the platform efficiently supports atomic 64 bit unsigned integers those are also provided. To implement atomics support for a platform/architecture/compiler for a type of atomics 32bit compare and exchange needs to be implemented. If available and more efficient native support for flags, 32 bit atomic addition, and corresponding 64 bit operations may also be provided. Additional useful atomic operations are implemented generically ontop of these. The implementation for various versions of gcc, msvc and sun studio have been tested. Additional existing stub implementations for * Intel icc * HUPX acc * IBM xlc are included but have never been tested. These will likely require fixes based on buildfarm and user feedback. As atomic operations also require barriers for some operations the existing barrier support has been moved into the atomics code. Author: Andres Freund with contributions from Oskari Saarenmaa Reviewed-By: Amit Kapila, Robert Haas, Heikki Linnakangas and Álvaro Herrera Discussion: CA+TgmoYBW+ux5-8Ja=Mcyuy8=VXAnVRHp3Kess6Pn3DMXAPAEA@mail.gmail.com, 20131015123303.GH5300@awork2.anarazel.de, 20131028205522.GI20248@awork2.anarazel.de		11 years ago
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Makefile	Remove cvs keywords from all files.	15 years ago
ac_func_accept_argtypes.m4	Enable compiling with the mingw-w64 32 bit compiler.	14 years ago
acx_pthread.m4	Remove some useless code in the configure script.	11 years ago
c-compiler.m4	Add a basic atomic ops API abstracting away platform/architecture details.	11 years ago
c-library.m4	Fix configure check for %z printf support after INT64_MODIFIER changes.	11 years ago
config.guess	Update config.guess and config.sub	12 years ago
config.sub	Update config.guess and config.sub	12 years ago
docbook.m4	Fix configure's search for collateindex.pl.	14 years ago
general.m4	Remove useless whitespace at end of lines	15 years ago
install-sh	Fix install-strip on Mac OS X	13 years ago
libtool.m4	Rename AC_PROG_LD* macros to PGAC_PROG_LD*. This avoids clashes with the	21 years ago
missing	Remove cvs keywords from all files.	15 years ago
perl.m4	Detect Windows perl linkage parameters in configure script.	13 years ago
prep_buildtree	find -path is not portable, so use grep -v instead.	15 years ago
programs.m4	Move PGAC_LDAP_SAFE to config/programs.m4.	11 years ago
python.m4	On OS X, link libpython normally, ignoring the "framework" framework.	11 years ago
tcl.m4	Accept tcl 8.6 in configure's probe for tclsh.	12 years ago
test_quiet_include.h	pgindent run for 9.4	12 years ago