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2c78940527
This set of changes removes the list of available buffers and instead simply uses the clock-sweep algorithm to find and return an available buffer. This also removes the have_free_buffer() function and simply caps the pg_autoprewarm process to at most NBuffers. While on the surface this appears to be removing an optimization it is in fact eliminating code that induces overhead in the form of synchronization that is problematic for multi-core systems. The main reason for removing the freelist, however, is not the moderate improvement in scalability, but that having the freelist would require dedicated complexity in several upcoming patches. As we have not been able to find a case benefiting from the freelist... Author: Greg Burd <greg@burd.me> Reviewed-by: Tomas Vondra <tomas@vondra.me> Reviewed-by: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/70C6A5B5-2A20-4D0B-BC73-EB09DD62D61C@getmailspring.com
The PostgreSQL contrib tree
---------------------------
This subtree contains porting tools, analysis utilities, and plug-in
features that are not part of the core PostgreSQL system, mainly
because they address a limited audience or are too experimental to be
part of the main source tree. This does not preclude their
usefulness.
User documentation for each module appears in the main SGML
documentation.
When building from the source distribution, these modules are not
built automatically, unless you build the "world" target. You can
also build and install them all by running "make all" and "make
install" in this directory; or to build and install just one selected
module, do the same in that module's subdirectory.
Some directories supply new user-defined functions, operators, or
types. To make use of one of these modules, after you have installed
the code you need to register the new SQL objects in the database
system by executing a CREATE EXTENSION command. In a fresh database,
you can simply do
CREATE EXTENSION module_name;
See the PostgreSQL documentation for more information about this
procedure.