From 1be203519ac4da238bf6dfe8f7015d5780723e0f Mon Sep 17 00:00:00 2001
From: Simon Riggs <simon@2ndQuadrant.com>
Date: Sun, 7 Apr 2013 22:37:39 +0100
Subject: [PATCH] Tune BufferGetLSNAtomic() when checksums !enabled

From performance analysis by Heikki Linnakangas
---
 src/backend/storage/buffer/bufmgr.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 1cd0ac806a..c2ef53f461 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -2079,8 +2079,10 @@ BufferGetLSNAtomic(Buffer buffer)
 	char				*page = BufferGetPage(buffer);
 	XLogRecPtr			 lsn;
 
-	/* Local buffers don't need a lock. */
-	if (BufferIsLocal(buffer))
+	/*
+	 * If we don't need locking for correctness, fastpath out.
+	 */
+	if (!DataChecksumsEnabled() || BufferIsLocal(buffer))
 		return PageGetLSN(page);
 
 	/* Make sure we've got a real buffer, and that we hold a pin on it. */