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From: Bertrand Drouvot <[email protected]>
Subject: [PATCH v1 1/2] Use C11 alignas in typedef definitions
Date: Tue, 24 Feb 2026 09:21:19 +0000

They were already using pg_attribute_aligned.  This replaces that with
alignas and moves that into the required syntactic position.

Suggested-by: Peter Eisentraut <[email protected]>
Author: Bertrand Drouvot <[email protected]>
Discussion: https://postgr.es/m/d7a788fa-e609-4894-a8be-2f70e135424f%40eisentraut.org
---
 src/backend/storage/aio/method_io_uring.c | 16 ++++++++--------
 src/include/storage/proc.h                | 13 +++++--------
 2 files changed, 13 insertions(+), 16 deletions(-)
  58.1% src/backend/storage/aio/
  41.8% src/include/storage/

diff --git a/src/backend/storage/aio/method_io_uring.c b/src/backend/storage/aio/method_io_uring.c
index ed6e71bcd46..50ea9f8e51c 100644
--- a/src/backend/storage/aio/method_io_uring.c
+++ b/src/backend/storage/aio/method_io_uring.c
@@ -77,15 +77,15 @@ const IoMethodOps pgaio_uring_ops = {
 	.wait_one = pgaio_uring_wait_one,
 };
 
-/*
- * Per-backend state when using io_method=io_uring
- *
- * Align the whole struct to a cacheline boundary, to prevent false sharing
- * between completion_lock and prior backend's io_uring_ring.
- */
-typedef struct pg_attribute_aligned (PG_CACHE_LINE_SIZE)
-PgAioUringContext
+/* Per-backend state when using io_method=io_uring */
+typedef struct PgAioUringContext
 {
+	/*
+	 * Align the whole struct to a cacheline boundary, to prevent false
+	 * sharing between completion_lock and prior backend's io_uring_ring.
+	 */
+	alignas(PG_CACHE_LINE_SIZE)
+
 	/*
 	 * Multiple backends can process completions for this backend's io_uring
 	 * instance (e.g. when the backend issuing IO is busy doing something
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index a8d2e7db1a1..fe798d350f1 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -180,6 +180,11 @@ typedef enum
  */
 typedef struct PGPROC
 {
+	/*
+	 * Align the struct at cache line boundaries.  This is just for
+	 * performance, to avoid false sharing.
+	 */
+	alignas(PG_CACHE_LINE_SIZE)
 	dlist_head *procgloballist; /* procglobal list that owns this PGPROC */
 	dlist_node	freeProcsLink;	/* link in procgloballist, when in recycled
 								 * state */
@@ -375,14 +380,6 @@ typedef struct PGPROC
 
 	uint32		wait_event_info;	/* proc's wait information */
 }
-
-/*
- * 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;
-- 
2.34.1


--fe1S3SCuJMoalI5t
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v1-0002-Use-C11-alignas-in-more-tricky-typedef-definition.patch"

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