From: Heikki Linnakangas Date: Sun, 22 Feb 2026 11:13:43 +0000 (+0200) Subject: Align PGPROC to cache line boundary X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=412f78c66eedbe9cf41a657f4566d86a69ab7af2;p=thirdparty%2Fpostgresql.git Align PGPROC to cache line boundary On common architectures, the PGPROC struct happened to be a multiple of 64 bytes on PG 18, but it's changed on 'master' since. There was worry that changing the alignment might hurt performance, due to false cacheline sharing across elements in the proc array. However, there was no explicit alignment, so any alignment to cache lines was accidental. Add explicit alignment to remove worry about false sharing. Reviewed-by: Bertrand Drouvot Discussion: https://www.postgresql.org/message-id/3dd6f70c-b94d-4428-8e75-74a7136396be@iki.fi --- diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h index b2fd4d02959..a8d2e7db1a1 100644 --- a/src/include/storage/proc.h +++ b/src/include/storage/proc.h @@ -374,8 +374,16 @@ typedef struct PGPROC ************************************************************************/ uint32 wait_event_info; /* proc's wait information */ -} PGPROC; +} +/* + * If compiler understands aligned pragma, use it to align the struct at cache + * line boundaries. This is just for performance, to avoid false sharing. + */ +#if defined(pg_attribute_aligned) + pg_attribute_aligned(PG_CACHE_LINE_SIZE) +#endif +PGPROC; extern PGDLLIMPORT PGPROC *MyProc;