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commit    412f78c66eedbe9cf41a657f4566d86a69ab7af2
Author:   Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date:     Sun Feb 22 11:13:43 2026 +0000

    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 <bertranddrouvot.pg@gmail.com>
    Discussion: https://www.postgresql.org/message-id/3dd6f70c-b94d-4428-8e75-74a7136396be@iki.fi


 src/include/storage/proc.h | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

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;
 


[parent: 2e0853176f8f]