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The new slab allocator needs different per-allocation information than the classical aset.c. The definition in 58b25e981 wasn't sufficiently careful on 32 platforms with 8 byte alignment, leading to buildfarm failures. That's not entirely easy to fix by just adjusting the definition. As slab.c doesn't actually need the size part(s) of the common header, all chunks are equally sized after all, it seems better to instead reduce the header to the part needed by all allocators, namely which context an allocation belongs to. That has the advantage of reducing the overhead of slab allocations, and also allows for more flexibility in future allocators. To avoid spreading the logic about accessing a chunk's context around, centralize it in GetMemoryChunkContext(), which allows to delete a good number of lines. A followup commit will revise the mmgr/README portion about StandardChunkHeader, and more. Author: Andres Freund Discussion: https://postgr.es/m/20170228074420.aazv4iw6k562mnxg@alap3.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/.