From: Heikki Linnakangas <heikki@enterprisedb.com>
Date: Tue, 27 Jan 2009 08:10:52 +0000 (+0200)
Subject: Remove padding in XLogCtl; might be a good idea, but let's keep it simple
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=f0fdc83d001e52de42114be1cf69f8a957d5b1ef;p=users%2Fsimon%2Fpostgres.git

Remove padding in XLogCtl; might be a good idea, but let's keep it simple
for now.

Also remove the XLogCtl->mode_lck spinlock, which is pretty pointless for
a single boolean that's only written by one process.
---

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 6b68791120..f311a9f3ce 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -317,18 +317,11 @@ typedef struct XLogCtlWrite
 
 /*
  * Total shared-memory state for XLOG.
- *
- * This small structure is accessed by many backends, so we take care to
- * pad out the parts of the structure so they can be accessed by separate
- * CPUs without causing false sharing cache flushes. Padding is generous
- * to allow for a wide variety of CPU architectures.
  */
-#define	XLOGCTL_BUFFER_SPACING	128
 typedef struct XLogCtlData
 {
 	/* Protected by WALInsertLock: */
 	XLogCtlInsert Insert;
-	char	InsertPadding[XLOGCTL_BUFFER_SPACING - sizeof(XLogCtlInsert)];
 
 	/* Protected by info_lck: */
 	XLogwrtRqst LogwrtRqst;
@@ -336,16 +329,9 @@ typedef struct XLogCtlData
 	uint32		ckptXidEpoch;	/* nextXID & epoch of latest checkpoint */
 	TransactionId ckptXid;
 	XLogRecPtr	asyncCommitLSN; /* LSN of newest async commit */
-	/* add data structure padding for above info_lck declarations */
-	char	InfoPadding[XLOGCTL_BUFFER_SPACING - sizeof(XLogwrtRqst) 
-											- sizeof(XLogwrtResult)
-											- sizeof(uint32)
-											- sizeof(TransactionId)
-											- sizeof(XLogRecPtr)];
 
 	/* Protected by WALWriteLock: */
 	XLogCtlWrite Write;
-	char	WritePadding[XLOGCTL_BUFFER_SPACING - sizeof(XLogCtlWrite)];
 
 	/*
 	 * These values do not change after startup, although the pointed-to pages
@@ -367,13 +353,8 @@ typedef struct XLogCtlData
 	 * always during Recovery Processing Mode. This allows us to identify
 	 * code executed *during* Recovery Processing Mode but not necessarily
 	 * by Startup process itself.
-	 *
-	 * Protected by mode_lck
 	 */
 	bool		SharedRecoveryProcessingMode;
-	slock_t		mode_lck;
-
-	char		InfoLockPadding[XLOGCTL_BUFFER_SPACING];
 
 	slock_t		info_lck;		/* locks shared variables shown above */
 } XLogCtlData;
@@ -4374,7 +4355,6 @@ XLOGShmemInit(void)
 	XLogCtl->XLogCacheBlck = XLOGbuffers - 1;
 	XLogCtl->Insert.currpage = (XLogPageHeader) (XLogCtl->pages);
 	SpinLockInit(&XLogCtl->info_lck);
-	SpinLockInit(&XLogCtl->mode_lck);
 
 	/*
 	 * If we are not in bootstrap mode, pg_control should already exist. Read