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The main optimization is for LockBufHdr() to delay initializing SpinDelayStatus, similar to what LWLockWaitListLock already did. The initialization is sufficiently expensive & buffer header lock acquisitions are sufficiently frequent, to make it worthwhile to instead have a fastpath (via a likely() branch) that does not initialize the SpinDelayStatus. While LWLockWaitListLock() already the aforementioned optimization, it did not use likely(), and inspection of the assembly shows that this indeed leads to worse code generation (also observed in a microbenchmark). Fix that by adding the likely(). While the LockBufHdr() improvement is a small gain on its own, it mainly is aimed at preventing a regression after a future commit, which requires additional locking to set hint bits. While touching both, also make the comments more similar to each other. Reviewed-by: Heikki Linnakangas <heikki.linnakangas@iki.fi> Discussion: https://postgr.es/m/fvfmkr5kk4nyex56ejgxj3uzi63isfxovp2biecb4bspbjrze7@az2pljabhnff
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.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.