4bc0f165cb
While beneficial, both for throughput and average/worst case latency, in a significant number of workloads, there are other workloads in which backend_flush_after can cause significant performance regressions in comparison to < 9.6 releases. The regression is most likely when the hot data set is bigger than shared buffers, but significantly smaller than the operating system's page cache. I personally think that the benefit of enabling backend flush control is considerably bigger than the potential downsides, but a fair argument can be made that not regressing is more important than improving performance/latency. As the latter is the consensus, change the default to 0. The other settings introduced in 428b1d6b2 do not have the same potential for regressions, so leave them enabled. Benchmarks leading up to changing the default have been performed by Mithun Cy, Ashutosh Sharma and Robert Haas. Discussion: CAD__OuhPmc6XH=wYRm_+Q657yQE88DakN4=Ybh2oveFasHkoeA@mail.gmail.com
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/.