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smgrzeroextend() uses FileFallocate() to efficiently extend files by multiple blocks. When extending by a small number of blocks, use FileZero() instead, as using posix_fallocate() for small numbers of blocks is inefficient for some file systems / operating systems. FileZero() is also used as the fallback for FileFallocate() on platforms / filesystems that don't support fallocate. A big advantage of using posix_fallocate() is that it typically won't cause dirty buffers in the kernel pagecache. So far the most common pattern in our code is that we smgrextend() a page full of zeroes and put the corresponding page into shared buffers, from where we later write out the actual contents of the page. If the kernel, e.g. due to memory pressure or elapsed time, already wrote back the all-zeroes page, this can lead to doubling the amount of writes reaching storage. There are no users of smgrzeroextend() as of this commit. That will follow in future commits. Reviewed-by: Melanie Plageman <melanieplageman@gmail.com> Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi> Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Reviewed-by: David Rowley <dgrowleyml@gmail.com> Reviewed-by: John Naylor <john.naylor@enterprisedb.com> Discussion: https://postgr.es/m/20221029025420.eplyow6k7tgu6he3@awork3.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: https://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 https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.