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The goal of separating hotly accessed per-backend data from PGPROC into PGXACT is to make accesses fast (GetSnapshotData() in particular). But delayChkpt is not actually accessed frequently; only when starting a checkpoint. As it is frequently modified (multiple times in the course of a single transaction), storing it in the same cacheline as hotly accessed data unnecessarily dirties a contended cacheline. Therefore move delayChkpt to PGPROC. This is part of a larger series of patches intending to improve GetSnapshotData() scalability. It is committed and pushed separately, as it is independently beneficial (small but measurable win, limited by the other frequent modifications of PGXACT). Author: Andres Freund Reviewed-By: Robert Haas, Thomas Munro, David Rowley Discussion: https://postgr.es/m/20200301083601.ews6hz5dduc3w2se@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: 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/.