v1-0001-Elimination-of-the-repetitive-code-at-SLRU-bootst.patch

From 62762bf4a86af76d845755e41f46714d2b41bbe4 Mon Sep 17 00:00:00 2001
From: Evgeny Voropaev <evorop@gmail.com>
Date: Thu, 13 Feb 2025 12:43:20 +0800
Subject: [PATCH v1] Elimination of the repetitive code at the SLRU bootstrap
 functions.

The functions bootstrapping SLRU pages had a lot of repetitive code. A new
realized function BootStrapSlruPage has moved a duplicating code into the
single place. Additionally, a new member ZeroFunc has been implemented in the
SlruCtlData structure. The ZeroFunc keeps a pointer to a function proper
for nullifying SLRU pages of a type defined by a corresponding SlruCtlData
object.

Author: Evgeny Voropaev <evgeny.voropaev@tantorlabs.com> <evorop@gmail.com>
---
 src/backend/access/transam/clog.c      | 43 ++++------------
 src/backend/access/transam/commit_ts.c | 38 ++++----------
 src/backend/access/transam/multixact.c | 71 +++++---------------------
 src/backend/access/transam/slru.c      | 34 ++++++++++++
 src/backend/access/transam/subtrans.c  | 35 +++++--------
 src/include/access/slru.h              |  8 +++
 6 files changed, 87 insertions(+), 142 deletions(-)

diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index 0d556c00b8c..d02a80378a1 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -102,14 +102,6 @@ TransactionIdToPage(TransactionId xid)
  */
 #define THRESHOLD_SUBTRANS_CLOG_OPT	5
 
-/*
- * Link to shared-memory data structures for CLOG control
- */
-static SlruCtlData XactCtlData;
-
-#define XactCtl (&XactCtlData)
-
-
 static int	ZeroCLOGPage(int64 pageno, bool writeXlog);
 static bool CLOGPagePrecedes(int64 page1, int64 page2);
 static void WriteZeroPageXlogRec(int64 pageno);
@@ -130,6 +122,14 @@ static void TransactionIdSetPageStatusInternal(TransactionId xid, int nsubxids,
 											   XLogRecPtr lsn, int64 pageno);
 
 
+/*
+ * Link to shared-memory data structures for CLOG control
+ */
+static SlruCtlData XactCtlData = { .ZeroPage = ZeroCLOGPage };
+
+#define XactCtl (&XactCtlData)
+
+
 /*
  * TransactionIdSetTreeStatus
  *
@@ -832,19 +832,7 @@ check_transaction_buffers(int *newval, void **extra, GucSource source)
 void
 BootStrapCLOG(void)
 {
-	int			slotno;
-	LWLock	   *lock = SimpleLruGetBankLock(XactCtl, 0);
-
-	LWLockAcquire(lock, LW_EXCLUSIVE);
-
-	/* Create and zero the first page of the commit log */
-	slotno = ZeroCLOGPage(0, false);
-
-	/* Make sure it's written out */
-	SimpleLruWritePage(XactCtl, slotno);
-	Assert(!XactCtl->shared->page_dirty[slotno]);
-
-	LWLockRelease(lock);
+	BootStrapSlruPage(XactCtl, 0);
 }
 
 /*
@@ -1114,19 +1102,8 @@ clog_redo(XLogReaderState *record)
 	if (info == CLOG_ZEROPAGE)
 	{
 		int64		pageno;
-		int			slotno;
-		LWLock	   *lock;
-
 		memcpy(&pageno, XLogRecGetData(record), sizeof(pageno));
-
-		lock = SimpleLruGetBankLock(XactCtl, pageno);
-		LWLockAcquire(lock, LW_EXCLUSIVE);
-
-		slotno = ZeroCLOGPage(pageno, false);
-		SimpleLruWritePage(XactCtl, slotno);
-		Assert(!XactCtl->shared->page_dirty[slotno]);
-
-		LWLockRelease(lock);
+		BootStrapSlruPage(XactCtl, pageno);
 	}
 	else if (info == CLOG_TRUNCATE)
 	{
diff --git a/src/backend/access/transam/commit_ts.c b/src/backend/access/transam/commit_ts.c
index 95049acd0b5..33ef6716535 100644
--- a/src/backend/access/transam/commit_ts.c
+++ b/src/backend/access/transam/commit_ts.c
@@ -77,13 +77,6 @@ TransactionIdToCTsPage(TransactionId xid)
 #define TransactionIdToCTsEntry(xid)	\
 	((xid) % (TransactionId) COMMIT_TS_XACTS_PER_PAGE)
 
-/*
- * Link to shared-memory data structures for CommitTs control
- */
-static SlruCtlData CommitTsCtlData;
-
-#define CommitTsCtl (&CommitTsCtlData)
-
 /*
  * We keep a cache of the last value set in shared memory.
  *
@@ -121,6 +114,13 @@ static void DeactivateCommitTs(void);
 static void WriteZeroPageXlogRec(int64 pageno);
 static void WriteTruncateXlogRec(int64 pageno, TransactionId oldestXid);
 
+/*
+ * Link to shared-memory data structures for CommitTs control
+ */
+static SlruCtlData CommitTsCtlData = { .ZeroPage = ZeroCommitTsPage };
+
+#define CommitTsCtl (&CommitTsCtlData)
+
 /*
  * TransactionTreeSetCommitTsData
  *
@@ -747,16 +747,7 @@ ActivateCommitTs(void)
 
 	/* Create the current segment file, if necessary */
 	if (!SimpleLruDoesPhysicalPageExist(CommitTsCtl, pageno))
-	{
-		LWLock	   *lock = SimpleLruGetBankLock(CommitTsCtl, pageno);
-		int			slotno;
-
-		LWLockAcquire(lock, LW_EXCLUSIVE);
-		slotno = ZeroCommitTsPage(pageno, false);
-		SimpleLruWritePage(CommitTsCtl, slotno);
-		Assert(!CommitTsCtl->shared->page_dirty[slotno]);
-		LWLockRelease(lock);
-	}
+		BootStrapSlruPage(CommitTsCtl, pageno);
 
 	/* Change the activation status in shared memory. */
 	LWLockAcquire(CommitTsLock, LW_EXCLUSIVE);
@@ -1023,19 +1014,8 @@ commit_ts_redo(XLogReaderState *record)
 	if (info == COMMIT_TS_ZEROPAGE)
 	{
 		int64		pageno;
-		int			slotno;
-		LWLock	   *lock;
-
 		memcpy(&pageno, XLogRecGetData(record), sizeof(pageno));
-
-		lock = SimpleLruGetBankLock(CommitTsCtl, pageno);
-		LWLockAcquire(lock, LW_EXCLUSIVE);
-
-		slotno = ZeroCommitTsPage(pageno, false);
-		SimpleLruWritePage(CommitTsCtl, slotno);
-		Assert(!CommitTsCtl->shared->page_dirty[slotno]);
-
-		LWLockRelease(lock);
+		BootStrapSlruPage(CommitTsCtl, pageno);
 	}
 	else if (info == COMMIT_TS_TRUNCATE)
 	{
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index 27ccdf9500f..5fb688d19a1 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -223,15 +223,6 @@ PreviousMultiXactId(MultiXactId multi)
 	return multi == FirstMultiXactId ? MaxMultiXactId : multi - 1;
 }
 
-/*
- * Links to shared-memory data structures for MultiXact control
- */
-static SlruCtlData MultiXactOffsetCtlData;
-static SlruCtlData MultiXactMemberCtlData;
-
-#define MultiXactOffsetCtl	(&MultiXactOffsetCtlData)
-#define MultiXactMemberCtl	(&MultiXactMemberCtlData)
-
 /*
  * MultiXact state shared across all backends.  All this state is protected
  * by MultiXactGenLock.  (We also use SLRU bank's lock of MultiXactOffset and
@@ -420,6 +411,14 @@ static void WriteMTruncateXlogRec(Oid oldestMultiDB,
 								  MultiXactOffset startTruncMemb,
 								  MultiXactOffset endTruncMemb);
 
+/*
+ * Links to shared-memory data structures for MultiXact control
+ */
+static SlruCtlData MultiXactOffsetCtlData = { .ZeroPage = &ZeroMultiXactOffsetPage };
+static SlruCtlData MultiXactMemberCtlData = { .ZeroPage = &ZeroMultiXactMemberPage };
+
+#define MultiXactOffsetCtl	(&MultiXactOffsetCtlData)
+#define MultiXactMemberCtl	(&MultiXactMemberCtlData)
 
 /*
  * MultiXactIdCreate
@@ -2033,32 +2032,8 @@ check_multixact_member_buffers(int *newval, void **extra, GucSource source)
 void
 BootStrapMultiXact(void)
 {
-	int			slotno;
-	LWLock	   *lock;
-
-	lock = SimpleLruGetBankLock(MultiXactOffsetCtl, 0);
-	LWLockAcquire(lock, LW_EXCLUSIVE);
-
-	/* Create and zero the first page of the offsets log */
-	slotno = ZeroMultiXactOffsetPage(0, false);
-
-	/* Make sure it's written out */
-	SimpleLruWritePage(MultiXactOffsetCtl, slotno);
-	Assert(!MultiXactOffsetCtl->shared->page_dirty[slotno]);
-
-	LWLockRelease(lock);
-
-	lock = SimpleLruGetBankLock(MultiXactMemberCtl, 0);
-	LWLockAcquire(lock, LW_EXCLUSIVE);
-
-	/* Create and zero the first page of the members log */
-	slotno = ZeroMultiXactMemberPage(0, false);
-
-	/* Make sure it's written out */
-	SimpleLruWritePage(MultiXactMemberCtl, slotno);
-	Assert(!MultiXactMemberCtl->shared->page_dirty[slotno]);
-
-	LWLockRelease(lock);
+	BootStrapSlruPage(MultiXactOffsetCtl, 0);
+	BootStrapSlruPage(MultiXactMemberCtl, 0);
 }
 
 /*
@@ -3401,36 +3376,14 @@ multixact_redo(XLogReaderState *record)
 	if (info == XLOG_MULTIXACT_ZERO_OFF_PAGE)
 	{
 		int64		pageno;
-		int			slotno;
-		LWLock	   *lock;
-
 		memcpy(&pageno, XLogRecGetData(record), sizeof(pageno));
-
-		lock = SimpleLruGetBankLock(MultiXactOffsetCtl, pageno);
-		LWLockAcquire(lock, LW_EXCLUSIVE);
-
-		slotno = ZeroMultiXactOffsetPage(pageno, false);
-		SimpleLruWritePage(MultiXactOffsetCtl, slotno);
-		Assert(!MultiXactOffsetCtl->shared->page_dirty[slotno]);
-
-		LWLockRelease(lock);
+		BootStrapSlruPage(MultiXactOffsetCtl, pageno);
 	}
 	else if (info == XLOG_MULTIXACT_ZERO_MEM_PAGE)
 	{
 		int64		pageno;
-		int			slotno;
-		LWLock	   *lock;
-
 		memcpy(&pageno, XLogRecGetData(record), sizeof(pageno));
-
-		lock = SimpleLruGetBankLock(MultiXactMemberCtl, pageno);
-		LWLockAcquire(lock, LW_EXCLUSIVE);
-
-		slotno = ZeroMultiXactMemberPage(pageno, false);
-		SimpleLruWritePage(MultiXactMemberCtl, slotno);
-		Assert(!MultiXactMemberCtl->shared->page_dirty[slotno]);
-
-		LWLockRelease(lock);
+		BootStrapSlruPage(MultiXactMemberCtl, pageno);
 	}
 	else if (info == XLOG_MULTIXACT_CREATE_ID)
 	{
diff --git a/src/backend/access/transam/slru.c b/src/backend/access/transam/slru.c
index 9ce628e62a5..b73bea16972 100644
--- a/src/backend/access/transam/slru.c
+++ b/src/backend/access/transam/slru.c
@@ -1850,3 +1850,37 @@ SlruSyncFileTag(SlruCtl ctl, const FileTag *ftag, char *path)
 	errno = save_errno;
 	return result;
 }
+
+/*
+ * BootStrapSlruPage is a workhorse for functions bootstraping
+ *  SLRU pages, including:
+ *		BootStrapMultiXact,
+ *		BootStrapCLOG,
+ *		ActivateCommitTs,
+ *		multixact_redo,
+ *		commit_ts_redo.
+ *
+ * It performs all of the rut such as acquiring a lock, zeroing,
+ * ensuring that bootstrapped page is written out, and releasing the lock.
+ *
+ * A caller has to provide a proper ZeroFunc in the ctl structure.
+ *
+ */
+void
+BootStrapSlruPage(SlruCtl ctl, int64 pageno)
+{
+	int			slotno;
+	LWLock	   *lock;
+
+	lock = SimpleLruGetBankLock(ctl, pageno);
+	LWLockAcquire(lock, LW_EXCLUSIVE);
+
+	/* Create and zero the page in SLRU */
+	slotno = ctl->ZeroPage(pageno, false);
+
+	/* Make sure it's written out */
+	SimpleLruWritePage(ctl, slotno);
+	Assert(!ctl->shared->page_dirty[slotno]);
+
+	LWLockRelease(lock);
+}
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index 15153618fad..bad2c15951b 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -66,18 +66,18 @@ TransactionIdToPage(TransactionId xid)
 #define TransactionIdToEntry(xid) ((xid) % (TransactionId) SUBTRANS_XACTS_PER_PAGE)
 
 
+static int	ZeroSUBTRANSPage(int64 pageno, bool unused);
+static bool SubTransPagePrecedes(int64 page1, int64 page2);
+
+
 /*
  * Link to shared-memory data structures for SUBTRANS control
  */
-static SlruCtlData SubTransCtlData;
+static SlruCtlData SubTransCtlData = { .ZeroPage = ZeroSUBTRANSPage };
 
 #define SubTransCtl  (&SubTransCtlData)
 
 
-static int	ZeroSUBTRANSPage(int64 pageno);
-static bool SubTransPagePrecedes(int64 page1, int64 page2);
-
-
 /*
  * Record the parent of a subtransaction in the subtrans log.
  */
@@ -269,19 +269,7 @@ check_subtrans_buffers(int *newval, void **extra, GucSource source)
 void
 BootStrapSUBTRANS(void)
 {
-	int			slotno;
-	LWLock	   *lock = SimpleLruGetBankLock(SubTransCtl, 0);
-
-	LWLockAcquire(lock, LW_EXCLUSIVE);
-
-	/* Create and zero the first page of the subtrans log */
-	slotno = ZeroSUBTRANSPage(0);
-
-	/* Make sure it's written out */
-	SimpleLruWritePage(SubTransCtl, slotno);
-	Assert(!SubTransCtl->shared->page_dirty[slotno]);
-
-	LWLockRelease(lock);
+	BootStrapSlruPage(SubTransCtl, 0);
 }
 
 /*
@@ -291,10 +279,15 @@ BootStrapSUBTRANS(void)
  * The slot number of the new page is returned.
  *
  * Control lock must be held at entry, and will be held at exit.
+ * 
+ * bool unused is a parameter required to provide matching of the 
+ * ZeroSUBTRANSPage function to the SlruCtlData.ZeroPage function type.
  */
 static int
-ZeroSUBTRANSPage(int64 pageno)
+ZeroSUBTRANSPage(int64 pageno, bool unused)
 {
+	(void)unused; /* Supress compiler warning*/
+
 	return SimpleLruZeroPage(SubTransCtl, pageno);
 }
 
@@ -335,7 +328,7 @@ StartupSUBTRANS(TransactionId oldestActiveXID)
 			prevlock = lock;
 		}
 
-		(void) ZeroSUBTRANSPage(startPage);
+		(void) ZeroSUBTRANSPage(startPage, false);
 		if (startPage == endPage)
 			break;
 
@@ -395,7 +388,7 @@ ExtendSUBTRANS(TransactionId newestXact)
 	LWLockAcquire(lock, LW_EXCLUSIVE);
 
 	/* Zero the page */
-	ZeroSUBTRANSPage(pageno);
+	ZeroSUBTRANSPage(pageno, false);
 
 	LWLockRelease(lock);
 }
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index e142800aab2..ec48355ac74 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -161,6 +161,13 @@ typedef struct SlruCtlData
 	 * it's always the same, it doesn't need to be in shared memory.
 	 */
 	char		Dir[64];
+
+	/*
+	 * Function for nulifying a page pointed by this SlruCtlData object
+	 * Signature: 
+	 * 				int ZeroPage(int64 pageno, bool writeXlog);
+	*/
+	int			(*ZeroPage) (int64, bool);
 } SlruCtlData;
 
 typedef SlruCtlData *SlruCtl;
@@ -214,5 +221,6 @@ extern bool SlruScanDirCbReportPresence(SlruCtl ctl, char *filename,
 extern bool SlruScanDirCbDeleteAll(SlruCtl ctl, char *filename, int64 segpage,
 								   void *data);
 extern bool check_slru_buffers(const char *name, int *newval);
+extern void BootStrapSlruPage(SlruCtl ctl, int64 pageno);
 
 #endif							/* SLRU_H */
-- 
2.47.1