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AllocSet contexts with different maxBlockSize values can have the same freeListIndex. When reusing a context from one of the context_freelists, we updated maxBlockSize, but we failed to adjust allocChunkLimit, even though that ordinarily depends on maxBlockSize. This could result in some allocations being put on an external block when they shouldn't have been, resulting in excessive malloc() calls, or if the allocChunkLimit was left set higher than it should be, allocations could have resulted in memory not being free()'d after pfree() due to the chunk having been put on a multi-chunk block (these would still later be cleaned up when the context is reset, so no memory leaks). The repercussions of this are only inefficient use of memory and perhaps some performance instability depending on which context happened to be top of the freelist when a new AllocSet context was created. To fix, we move the allocChunkLimit calculation code into a helper function and call that to reset the allocChunkLimit when reusing a context. Author: Chao Li <li.evan.chao@gmail.com> Reviewed-by: Donghang Lin <donghanglin@gmail.com> Reviewed-by: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/1D54961E-6BEF-411A-BFAD-610C3B18D7E7@gmail.com Backpatch-through: 14
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/.