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StrategyGetBuffer() has proven to be a bottleneck in a number of buffer acquisition heavy workloads. To some degree this has already been alleviated by 5d7962c6, but it still can be quite a heavy bottleneck. The problem is that in unfortunate usage patterns a single StrategyGetBuffer() call will have to look at a large number of buffers - in turn making it likely that the process will be put to sleep while still holding the spinlock. Replace most of the usage of the buffer_strategy_lock spinlock for the clock sweep by a atomic nextVictimBuffer variable. That variable, modulo NBuffers, is the current hand of the clock sweep. The buffer clock-sweep then only needs to acquire the spinlock after a wraparound. And even then only in the process that did the wrapping around. That alleviates nearly all the contention on the relevant spinlock, although significant contention on the cacheline can still exist. Reviewed-By: Robert Haas and Amit Kapila Discussion: 20141010160020.GG6670@alap3.anarazel.de, 20141027133218.GA2639@awork2.anarazel.de
PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: http://www.postgresql.org/download See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.