From: Jan Wieck <JanWieck@Yahoo.com>
Date: Thu, 13 Nov 2003 05:34:58 +0000 (+0000)
Subject: ARC strategy backed out ... sorry
X-Git-Tag: REL8_0_0BETA1~1701
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=923e994d7901d7c0268725e219002af3b2d40dfc;p=postgresql

ARC strategy backed out ... sorry

Jan
---

diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 47564a3002..36062d4e30 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -13,7 +13,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.266 2003/11/13 00:40:00 wieck Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.267 2003/11/13 05:34:57 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -33,7 +33,6 @@
 #include "commands/vacuum.h"
 #include "executor/executor.h"
 #include "miscadmin.h"
-#include "storage/buf_internals.h"
 #include "storage/freespace.h"
 #include "storage/sinval.h"
 #include "storage/smgr.h"
@@ -311,16 +310,8 @@ vacuum(VacuumStmt *vacstmt)
 			else
 				old_context = MemoryContextSwitchTo(anl_context);
 
-			/*
-			 * Tell the buffer replacement strategy that vacuum is
-			 * causing the IO
-			 */
-			StrategyHintVacuum(true);
-
 			analyze_rel(relid, vacstmt);
 
-			StrategyHintVacuum(false);
-
 			if (vacstmt->vacuum)
 				CommitTransactionCommand();
 			else
@@ -758,12 +749,6 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
 	SetQuerySnapshot();			/* might be needed for functions in
 								 * indexes */
 
-	/*
-	 * Tell the cache replacement strategy that vacuum is causing
-	 * all following IO
-	 */
-	StrategyHintVacuum(true);
-
 	/*
 	 * Check for user-requested abort.	Note we want this to be inside a
 	 * transaction, so xact.c doesn't issue useless WARNING.
@@ -778,7 +763,6 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
 							  ObjectIdGetDatum(relid),
 							  0, 0, 0))
 	{
-		StrategyHintVacuum(false);
 		CommitTransactionCommand();
 		return true;			/* okay 'cause no data there */
 	}
@@ -812,7 +796,6 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
 				(errmsg("skipping \"%s\" --- only table or database owner can vacuum it",
 						RelationGetRelationName(onerel))));
 		relation_close(onerel, lmode);
-		StrategyHintVacuum(false);
 		CommitTransactionCommand();
 		return false;
 	}
@@ -827,7 +810,6 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
 				(errmsg("skipping \"%s\" --- cannot vacuum indexes, views, or special system tables",
 						RelationGetRelationName(onerel))));
 		relation_close(onerel, lmode);
-		StrategyHintVacuum(false);
 		CommitTransactionCommand();
 		return false;
 	}
@@ -842,7 +824,6 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
 	if (isOtherTempNamespace(RelationGetNamespace(onerel)))
 	{
 		relation_close(onerel, lmode);
-		StrategyHintVacuum(false);
 		CommitTransactionCommand();
 		return true;			/* assume no long-lived data in temp
 								 * tables */
@@ -882,7 +863,6 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
 	/*
 	 * Complete the transaction and free all temporary memory used.
 	 */
-	StrategyHintVacuum(false);
 	CommitTransactionCommand();
 
 	/*
diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c
index 616338c60c..79683b725c 100644
--- a/src/backend/storage/buffer/buf_init.c
+++ b/src/backend/storage/buffer/buf_init.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_init.c,v 1.55 2003/11/13 00:40:01 wieck Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_init.c,v 1.56 2003/11/13 05:34:58 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -48,6 +48,9 @@ long	   *CurTraceBuf;
 int			ShowPinTrace = 0;
 
 int			Data_Descriptors;
+int			Free_List_Descriptor;
+int			Lookup_List_Descriptor;
+int			Num_Descriptors;
 
 BufferDesc *BufferDescriptors;
 Block	   *BufferBlockPointers;
@@ -130,6 +133,9 @@ InitBufferPool(void)
 	int			i;
 
 	Data_Descriptors = NBuffers;
+	Free_List_Descriptor = Data_Descriptors;
+	Lookup_List_Descriptor = Data_Descriptors + 1;
+	Num_Descriptors = Data_Descriptors + 1;
 
 	/*
 	 * It's probably not really necessary to grab the lock --- if there's
@@ -150,7 +156,7 @@ InitBufferPool(void)
 
 	BufferDescriptors = (BufferDesc *)
 		ShmemInitStruct("Buffer Descriptors",
-					  Data_Descriptors * sizeof(BufferDesc), &foundDescs);
+					  Num_Descriptors * sizeof(BufferDesc), &foundDescs);
 
 	BufferBlocks = (char *)
 		ShmemInitStruct("Buffer Blocks",
@@ -170,14 +176,16 @@ InitBufferPool(void)
 		block = BufferBlocks;
 
 		/*
-		 * link the buffers into a single linked list. This will become the
-		 * LiFo list of unused buffers returned by StragegyGetBuffer().
+		 * link the buffers into a circular, doubly-linked list to
+		 * initialize free list, and initialize the buffer headers. Still
+		 * don't know anything about replacement strategy in this file.
 		 */
 		for (i = 0; i < Data_Descriptors; block += BLCKSZ, buf++, i++)
 		{
 			Assert(ShmemIsValid((unsigned long) block));
 
-			buf->bufNext = i + 1;
+			buf->freeNext = i + 1;
+			buf->freePrev = i - 1;
 
 			CLEAR_BUFFERTAG(&(buf->tag));
 			buf->buf_id = i;
@@ -191,12 +199,14 @@ InitBufferPool(void)
 			buf->wait_backend_id = 0;
 		}
 
-		/* Correct last entry */
-		BufferDescriptors[Data_Descriptors - 1].bufNext = -1;
+		/* close the circular queue */
+		BufferDescriptors[0].freePrev = Data_Descriptors - 1;
+		BufferDescriptors[Data_Descriptors - 1].freeNext = 0;
 	}
 
 	/* Init other shared buffer-management stuff */
-	StrategyInitialize(!foundDescs);
+	InitBufTable();
+	InitFreeList(!foundDescs);
 
 	LWLockRelease(BufMgrLock);
 }
diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c
index a2318a29f3..95db86c534 100644
--- a/src/backend/storage/buffer/buf_table.c
+++ b/src/backend/storage/buffer/buf_table.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_table.c,v 1.30 2003/11/13 00:40:01 wieck Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_table.c,v 1.31 2003/11/13 05:34:58 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -38,7 +38,7 @@ static HTAB *SharedBufHash;
  * Initialize shmem hash table for mapping buffers
  */
 void
-InitBufTable(int size)
+InitBufTable(void)
 {
 	HASHCTL		info;
 
@@ -50,7 +50,7 @@ InitBufTable(int size)
 	info.hash = tag_hash;
 
 	SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table",
-								  size, size,
+								  NBuffers, NBuffers,
 								  &info,
 								  HASH_ELEM | HASH_FUNCTION);
 
@@ -58,63 +58,79 @@ InitBufTable(int size)
 		elog(FATAL, "could not initialize shared buffer hash table");
 }
 
-/*
- * BufTableLookup
- */
-int
+BufferDesc *
 BufTableLookup(BufferTag *tagPtr)
 {
 	BufferLookupEnt *result;
 
 	if (tagPtr->blockNum == P_NEW)
-		return -1;
+		return NULL;
 
 	result = (BufferLookupEnt *)
 		hash_search(SharedBufHash, (void *) tagPtr, HASH_FIND, NULL);
 	if (!result)
-		return -1;
+		return NULL;
 
-	return result->id;
+	return &(BufferDescriptors[result->id]);
 }
 
 /*
  * BufTableDelete
  */
 bool
-BufTableInsert(BufferTag *tagPtr, Buffer buf_id)
+BufTableDelete(BufferDesc *buf)
 {
 	BufferLookupEnt *result;
-	bool		found;
 
-	result = (BufferLookupEnt *)
-		hash_search(SharedBufHash, (void *) tagPtr, HASH_ENTER, &found);
+	/*
+	 * buffer not initialized or has been removed from table already.
+	 * BM_DELETED keeps us from removing buffer twice.
+	 */
+	if (buf->flags & BM_DELETED)
+		return TRUE;
 
-	if (!result)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of shared memory")));
+	buf->flags |= BM_DELETED;
 
-	if (found)					/* found something else in the table? */
+	result = (BufferLookupEnt *)
+		hash_search(SharedBufHash, (void *) &(buf->tag), HASH_REMOVE, NULL);
+
+	if (!result)				/* shouldn't happen */
 		elog(ERROR, "shared buffer hash table corrupted");
 
-	result->id = buf_id;
+	/*
+	 * Clear the buffer's tag.  This doesn't matter for the hash table,
+	 * since the buffer is already removed from it, but it ensures that
+	 * sequential searches through the buffer table won't think the buffer
+	 * is still valid for its old page.
+	 */
+	buf->tag.rnode.relNode = InvalidOid;
+	buf->tag.rnode.tblNode = InvalidOid;
+
 	return TRUE;
 }
 
-/*
- * BufTableDelete
- */
 bool
-BufTableDelete(BufferTag *tagPtr)
+BufTableInsert(BufferDesc *buf)
 {
 	BufferLookupEnt *result;
+	bool		found;
+
+	/* cannot insert it twice */
+	Assert(buf->flags & BM_DELETED);
+	buf->flags &= ~(BM_DELETED);
 
 	result = (BufferLookupEnt *)
-		hash_search(SharedBufHash, (void *) tagPtr, HASH_REMOVE, NULL);
+		hash_search(SharedBufHash, (void *) &(buf->tag), HASH_ENTER, &found);
 
-	if (!result)				/* shouldn't happen */
+	if (!result)
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of shared memory")));
+
+	if (found)					/* found something else in the table? */
 		elog(ERROR, "shared buffer hash table corrupted");
 
+	result->id = buf->buf_id;
 	return TRUE;
 }
 
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index f10ff7e5b7..5613966616 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.142 2003/11/13 00:40:01 wieck Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.143 2003/11/13 05:34:58 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -260,8 +260,12 @@ ReadBufferInternal(Relation reln, BlockNumber blockNum,
 	if (status == SM_FAIL)
 	{
 		/* IO Failed.  cleanup the data structures and go home */
-		StrategyInvalidateBuffer(bufHdr);
 
+		if (!BufTableDelete(bufHdr))
+		{
+			LWLockRelease(BufMgrLock);
+			elog(FATAL, "buffer table broken after I/O error");
+		}
 		/* remember that BufferAlloc() pinned the buffer */
 		UnpinBuffer(bufHdr);
 
@@ -314,7 +318,7 @@ BufferAlloc(Relation reln,
 	INIT_BUFFERTAG(&newTag, reln, blockNum);
 
 	/* see if the block is in the buffer pool already */
-	buf = StrategyBufferLookup(&newTag, false);
+	buf = BufTableLookup(&newTag);
 	if (buf != NULL)
 	{
 		/*
@@ -375,7 +379,7 @@ BufferAlloc(Relation reln,
 	inProgress = FALSE;
 	for (buf = (BufferDesc *) NULL; buf == (BufferDesc *) NULL;)
 	{
-		buf = StrategyGetBuffer();
+		buf = GetFreeBuffer();
 
 		/* GetFreeBuffer will abort if it can't find a free buffer */
 		Assert(buf);
@@ -488,7 +492,7 @@ BufferAlloc(Relation reln,
 			 * we haven't gotten around to insert the new tag into the
 			 * buffer table. So we need to check here.		-ay 3/95
 			 */
-			buf2 = StrategyBufferLookup(&newTag, true);
+			buf2 = BufTableLookup(&newTag);
 			if (buf2 != NULL)
 			{
 				/*
@@ -531,12 +535,29 @@ BufferAlloc(Relation reln,
 	 */
 
 	/*
-	 * Tell the buffer replacement strategy that we are replacing the
-	 * buffer content. Then rename the buffer.
+	 * Change the name of the buffer in the lookup table:
+	 *
+	 * Need to update the lookup table before the read starts. If someone
+	 * comes along looking for the buffer while we are reading it in, we
+	 * don't want them to allocate a new buffer.  For the same reason, we
+	 * didn't want to erase the buf table entry for the buffer we were
+	 * writing back until now, either.
 	 */
-	StrategyReplaceBuffer(buf, reln, blockNum);
+
+	if (!BufTableDelete(buf))
+	{
+		LWLockRelease(BufMgrLock);
+		elog(FATAL, "buffer wasn't in the buffer hash table");
+	}
+
 	INIT_BUFFERTAG(&(buf->tag), reln, blockNum);
 
+	if (!BufTableInsert(buf))
+	{
+		LWLockRelease(BufMgrLock);
+		elog(FATAL, "buffer in buffer hash table twice");
+	}
+
 	/*
 	 * Buffer contents are currently invalid.  Have to mark IO IN PROGRESS
 	 * so no one fiddles with them until the read completes.  If this
@@ -688,28 +709,13 @@ BufferSync(void)
 	BufferDesc *bufHdr;
 	ErrorContextCallback errcontext;
 
-	int			num_buffer_dirty;
-	int		   *buffer_dirty;
-
 	/* Setup error traceback support for ereport() */
 	errcontext.callback = buffer_write_error_callback;
 	errcontext.arg = NULL;
 	errcontext.previous = error_context_stack;
 	error_context_stack = &errcontext;
 
-	/*
-	 * Get a list of all currently dirty buffers and how many there are.
-	 * We do not flush buffers that get dirtied after we started. They
-	 * have to wait until the next checkpoint.
-	 */
-	buffer_dirty = (int *)palloc(NBuffers * sizeof(int));
-	num_buffer_dirty = 0;
-
-	LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
-	num_buffer_dirty = StrategyDirtyBufferList(buffer_dirty, NBuffers);
-	LWLockRelease(BufMgrLock);
-
-	for (i = 0; i < num_buffer_dirty; i++)
+	for (i = 0, bufHdr = BufferDescriptors; i < NBuffers; i++, bufHdr++)
 	{
 		Buffer		buffer;
 		int			status;
@@ -717,11 +723,10 @@ BufferSync(void)
 		XLogRecPtr	recptr;
 		Relation	reln;
 
-		LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
-
-		bufHdr = &BufferDescriptors[buffer_dirty[i]];
 		errcontext.arg = bufHdr;
 
+		LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
+
 		if (!(bufHdr->flags & BM_VALID))
 		{
 			LWLockRelease(BufMgrLock);
@@ -850,8 +855,6 @@ BufferSync(void)
 			RelationDecrementReferenceCount(reln);
 	}
 
-	pfree(buffer_dirty);
-
 	/* Pop the error context stack */
 	error_context_stack = errcontext.previous;
 }
@@ -956,9 +959,9 @@ AtEOXact_Buffers(bool isCommit)
 
 			if (isCommit)
 				elog(WARNING,
-				"buffer refcount leak: [%03d] (bufNext=%d, "
+				"buffer refcount leak: [%03d] (freeNext=%d, freePrev=%d, "
 				  "rel=%u/%u, blockNum=%u, flags=0x%x, refcount=%d %ld)",
-					 i, buf->bufNext,
+					 i, buf->freeNext, buf->freePrev,
 					 buf->tag.rnode.tblNode, buf->tag.rnode.relNode,
 					 buf->tag.blockNum, buf->flags,
 					 buf->refcount, PrivateRefCount[i]);
@@ -1226,7 +1229,7 @@ recheck:
 			/*
 			 * And mark the buffer as no longer occupied by this rel.
 			 */
-			StrategyInvalidateBuffer(bufHdr);
+			BufTableDelete(bufHdr);
 		}
 	}
 
@@ -1292,7 +1295,7 @@ recheck:
 			/*
 			 * And mark the buffer as no longer occupied by this page.
 			 */
-			StrategyInvalidateBuffer(bufHdr);
+			BufTableDelete(bufHdr);
 		}
 	}
 
@@ -1540,7 +1543,7 @@ FlushRelationBuffers(Relation rel, BlockNumber firstDelBlock)
 				return -2;
 			}
 			if (bufHdr->tag.blockNum >= firstDelBlock)
-				StrategyInvalidateBuffer(bufHdr);
+				BufTableDelete(bufHdr);
 		}
 	}
 
diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 9e340b4720..ac8931752d 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -1,14 +1,15 @@
 /*-------------------------------------------------------------------------
  *
  * freelist.c
- *	  routines for manipulating the buffer pool's replacement strategy.
+ *	  routines for manipulating the buffer pool's replacement strategy
+ *	  freelist.
  *
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/freelist.c,v 1.32 2003/11/13 00:40:01 wieck Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/freelist.c,v 1.33 2003/11/13 05:34:58 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -30,814 +31,55 @@
 #include "storage/bufmgr.h"
 #include "storage/ipc.h"
 #include "storage/proc.h"
-#include "access/xact.h"
 
-#define STRAT_LIST_UNUSED	-1
-#define STRAT_LIST_B1		0
-#define STRAT_LIST_T1		1
-#define STRAT_LIST_T2		2
-#define STRAT_LIST_B2		3
-#define STRAT_NUM_LISTS		4
-
-#ifndef MAX
-#define MAX(a,b) (((a) > (b)) ? (a) : (b))
-#endif
-#ifndef MIN
-#define MIN(a,b) (((a) < (b)) ? (a) : (b))
-#endif
-
-/*
- * The Cache Directory Block (CDB) of the Adaptive Replacement Cache (ARC)
- */
-typedef struct bufstratcdb
-{
-	int				prev;		/* links in the queue */
-	int				next;
-	int				list;		/* current list */
-	BufferTag		buf_tag;	/* buffer key */
-	Buffer			buf_id;		/* currently assigned data buffer */
-	TransactionId	t1_xid;		/* the xid this entry went onto T1 */
-} BufferStrategyCDB;
-
-/*
- * The shared ARC control information.
- */
-typedef struct bufstratcontrol
-{
-
-	int		target_T1_size;				/* What T1 size are we aiming for */
-	int		listUnusedCDB;				/* All unused StrategyCDB */
-	int		listHead[STRAT_NUM_LISTS];	/* ARC lists B1, T1, T2 and B2 */
-	int		listTail[STRAT_NUM_LISTS];
-	int		listSize[STRAT_NUM_LISTS];
-	Buffer	listFreeBuffers;			/* List of unused buffers */
-
-	long	num_lookup;					/* Some hit statistics */
-	long	num_hit[STRAT_NUM_LISTS];
-	time_t	stat_report;
-
-	BufferStrategyCDB	cdb[1];			/* The cache directory */
-} BufferStrategyControl;
- 
-
-static BufferStrategyControl	*StrategyControl = NULL;
-static BufferStrategyCDB		*StrategyCDB = NULL;
-
-static int		strategy_cdb_found;
-static int		strategy_cdb_replace;
-static int		strategy_get_from;
-
-int				BufferStrategyStatInterval = 0;
-
-static bool				strategy_hint_vacuum;
-static TransactionId	strategy_vacuum_xid;
-
-
-#define T1_TARGET	StrategyControl->target_T1_size
-#define B1_LENGTH	StrategyControl->listSize[STRAT_LIST_B1]
-#define T1_LENGTH	StrategyControl->listSize[STRAT_LIST_T1]
-#define T2_LENGTH	StrategyControl->listSize[STRAT_LIST_T2]
-#define B2_LENGTH	StrategyControl->listSize[STRAT_LIST_B2]
 
+static BufferDesc *SharedFreeList;
 
 /*
- * Macro to remove a CDB from whichever list it currently is on
+ * State-checking macros
  */
-#define	STRAT_LIST_REMOVE(cdb) \
-{ \
-	AssertMacro((cdb)->list >= 0 && (cdb)->list < STRAT_NUM_LISTS);		\
-	if ((cdb)->prev < 0)												\
-		StrategyControl->listHead[(cdb)->list] = (cdb)->next;			\
-	else																\
-		StrategyCDB[(cdb)->prev].next = (cdb)->next;					\
-	if ((cdb)->next < 0)												\
-		StrategyControl->listTail[(cdb)->list] = (cdb)->prev;			\
-	else																\
-		StrategyCDB[(cdb)->next].prev = (cdb)->prev;					\
-	StrategyControl->listSize[(cdb)->list]--;							\
-	(cdb)->list = STRAT_LIST_UNUSED;									\
-}
 
-/*
- * Macro to add a CDB to the tail of a list (MRU position)
- */
-#define STRAT_MRU_INSERT(cdb,l) \
-{ \
-	AssertMacro((cdb)->list == STRAT_LIST_UNUSED);						\
-	if (StrategyControl->listTail[(l)] < 0)								\
-	{																	\
-		(cdb)->prev = (cdb)->next = -1;									\
-		StrategyControl->listHead[(l)] = 								\
-			StrategyControl->listTail[(l)] =							\
-			((cdb) - StrategyCDB);										\
-	}																	\
-	else																\
-	{																	\
-		(cdb)->next = -1;												\
-		(cdb)->prev = StrategyControl->listTail[(l)];					\
-		StrategyCDB[StrategyControl->listTail[(l)]].next = 				\
-			((cdb) - StrategyCDB);										\
-		StrategyControl->listTail[(l)] = 								\
-			((cdb) - StrategyCDB);										\
-	}																	\
-	StrategyControl->listSize[(l)]++;									\
-	(cdb)->list = (l);													\
-}
+#define IsInQueue(bf) \
+( \
+	AssertMacro((bf->freeNext != INVALID_DESCRIPTOR)), \
+	AssertMacro((bf->freePrev != INVALID_DESCRIPTOR)), \
+	AssertMacro((bf->flags & BM_FREE)) \
+)
 
-/*
- * Macro to add a CDB to the head of a list (LRU position)
- */
-#define STRAT_LRU_INSERT(cdb,l) \
-{ \
-	AssertMacro((cdb)->list == STRAT_LIST_UNUSED);						\
-	if (StrategyControl->listHead[(l)] < 0)								\
-	{																	\
-		(cdb)->prev = (cdb)->next = -1;									\
-		StrategyControl->listHead[(l)] = 								\
-			StrategyControl->listTail[(l)] =							\
-			((cdb) - StrategyCDB);										\
-	}																	\
-	else																\
-	{																	\
-		(cdb)->prev = -1;												\
-		(cdb)->next = StrategyControl->listHead[(l)];					\
-		StrategyCDB[StrategyControl->listHead[(l)]].prev = 				\
-			((cdb) - StrategyCDB);										\
-		StrategyControl->listHead[(l)] = 								\
-			((cdb) - StrategyCDB);										\
-	}																	\
-	StrategyControl->listSize[(l)]++;									\
-	(cdb)->list = (l);													\
-}
+#define IsNotInQueue(bf) \
+( \
+	AssertMacro((bf->freeNext == INVALID_DESCRIPTOR)), \
+	AssertMacro((bf->freePrev == INVALID_DESCRIPTOR)), \
+	AssertMacro(! (bf->flags & BM_FREE)) \
+)
 
 
 /*
- * StrategyBufferLookup
+ * AddBufferToFreelist
  *
- *	Lookup a page request in the cache directory. A buffer is only
- *	returned for a T1 or T2 cache hit. B1 and B2 hits are only
- *	remembered here to later affect the behaviour.
+ * In theory, this is the only routine that needs to be changed
+ * if the buffer replacement strategy changes.	Just change
+ * the manner in which buffers are added to the freelist queue.
+ * Currently, they are added on an LRU basis.
  */
-BufferDesc *
-StrategyBufferLookup(BufferTag *tagPtr, bool recheck)
-{
-	BufferStrategyCDB  *cdb;
-	time_t				now;
-
-	if (BufferStrategyStatInterval > 0)
-	{
-		time(&now);
-		if (StrategyControl->stat_report + BufferStrategyStatInterval < now)
-		{
-			long	all_hit, b1_hit, t1_hit, t2_hit, b2_hit;
-			ErrorContextCallback	*errcxtold;
-
-			if (StrategyControl->num_lookup == 0)
-			{
-				all_hit = b1_hit = t1_hit = t2_hit = b2_hit = 0;
-			}
-			else
-			{
-				b1_hit = (StrategyControl->num_hit[STRAT_LIST_B1] * 100 /
-						  StrategyControl->num_lookup);
-				t1_hit = (StrategyControl->num_hit[STRAT_LIST_T1] * 100 /
-						  StrategyControl->num_lookup);
-				t2_hit = (StrategyControl->num_hit[STRAT_LIST_T2] * 100 /
-						  StrategyControl->num_lookup);
-				b2_hit = (StrategyControl->num_hit[STRAT_LIST_B2] * 100 /
-						  StrategyControl->num_lookup);
-				all_hit = b1_hit + t1_hit + t2_hit + b2_hit;
-			}
-
-			errcxtold = error_context_stack;
-			error_context_stack = NULL;
-			elog(DEBUG1, "ARC T1target=%5d B1len=%5d T1len=%5d T2len=%5d B2len=%5d",
-					T1_TARGET, B1_LENGTH, T1_LENGTH, T2_LENGTH, B2_LENGTH);
-			elog(DEBUG1, "ARC total   =%4ld%% B1hit=%4ld%% T1hit=%4ld%% T2hit=%4ld%% B2hit=%4ld%%",
-					all_hit, b1_hit, t1_hit, t2_hit, b2_hit);
-			error_context_stack = errcxtold;
-
-			StrategyControl->num_lookup = 0;
-			StrategyControl->num_hit[STRAT_LIST_B1] = 0;
-			StrategyControl->num_hit[STRAT_LIST_T1] = 0;
-			StrategyControl->num_hit[STRAT_LIST_T2] = 0;
-			StrategyControl->num_hit[STRAT_LIST_B2] = 0;
-			StrategyControl->stat_report = now;
-		}
-	}
-
-	/*
-	 * Count lookups
-	 */
-	StrategyControl->num_lookup++;
-
-	/*
-	 * Lookup the block in the shared hash table
-	 */
-	strategy_cdb_found = BufTableLookup(tagPtr);
-
-	/*
-	 * Handle CDB lookup miss
-	 */
-	if (strategy_cdb_found < 0)
-	{
-		if (!recheck)
-		{
-			/*
-			 * This is an initial lookup and we have a complete
-			 * cache miss (block found nowhere). This means we
-			 * remember according to the current T1 size and the
-			 * target T1 size from where we take a block if we
-			 * need one later.
-			 */
-			if (T1_LENGTH >= MAX(1, T1_TARGET))
-				strategy_get_from = STRAT_LIST_T1;
-			else
-				strategy_get_from = STRAT_LIST_T2;
-		}
-
-		/* report cache miss */
-		return NULL;
-	}
-
-	/*
-	 * We found a CDB
-	 */
-	cdb = &StrategyCDB[strategy_cdb_found];
-
-	/*
-	 * Count hits
-	 */
-	StrategyControl->num_hit[cdb->list]++;
-
-	/*
-	 * If this is a T2 hit, we simply move the CDB to the
-	 * T2 MRU position and return the found buffer.
-	 */
-	if (cdb->list == STRAT_LIST_T2)
-	{
-		STRAT_LIST_REMOVE(cdb);
-		STRAT_MRU_INSERT(cdb, STRAT_LIST_T2);
-
-		return &BufferDescriptors[cdb->buf_id];
-	}
-
-	/*
-	 * If this is a T1 hit, we move the buffer to the T2 MRU
-	 * only if another transaction had read it into T1. This is
-	 * required because any UPDATE or DELETE in PostgreSQL does
-	 * multiple ReadBuffer(), first during the scan, later during
-	 * the heap_update() or heap_delete().
-	 */
-	if (cdb->list == STRAT_LIST_T1)
-	{
-		if (!TransactionIdIsCurrentTransactionId(cdb->t1_xid))
-		{
-			STRAT_LIST_REMOVE(cdb);
-			STRAT_MRU_INSERT(cdb, STRAT_LIST_T2);
-		}
-
-		return &BufferDescriptors[cdb->buf_id];
-	}
-
-	/*
-	 * In the case of a recheck we don't care about B1 or B2 hits here.
-	 * The bufmgr does this call only to make sure noone faulted in the
-	 * block while we where busy flushing another. Now for this really
-	 * to end up as a B1 or B2 cache hit, we must have been flushing for
-	 * quite some time as the block not only must have been read, but
-	 * also traveled through the queue and evicted from the T cache again
-	 * already. 
-	 */
-	if (recheck)
-		return NULL;
-
-	/*
-	 * Adjust the target size of the T1 cache depending on if this is
-	 * a B1 or B2 hit.
-	 */
-	switch (cdb->list)
-	{
-		case STRAT_LIST_B1:
-			/*
-			 * B1 hit means that the T1 cache is probably too
-			 * small. Adjust the T1 target size and continue
-			 * below.
-			 */
-			T1_TARGET = MIN(T1_TARGET + MAX(B2_LENGTH / B1_LENGTH, 1),
-							Data_Descriptors);
-			break;
-
-		case STRAT_LIST_B2:
-			/* 
-			 * B2 hit means that the T2 cache is probably too
-			 * small. Adjust the T1 target size and continue
-			 * below.
- */
-			T1_TARGET = MAX(T1_TARGET - MAX(B1_LENGTH / B2_LENGTH, 1), 0);
-			break;
-
-		default:
-			elog(ERROR, "Buffer hash table corrupted - CDB on list %d found",
-					cdb->list);
-	}
-
-	/*
-	 * Decide where to take from if we will be out of
-	 * free blocks later in StrategyGetBuffer().
-	 */
-	if (T1_LENGTH >= MAX(1, T1_TARGET))
-		strategy_get_from = STRAT_LIST_T1;
-	else
-		strategy_get_from = STRAT_LIST_T2;
-
-	/*
-	 * Even if we had seen the block in the past, it's data is
-	 * not currently in memory ... cache miss to the bufmgr.
-	 */
-	return NULL;
-}
-
-
-/*
- * StrategyGetBuffer
- *
- *	Called by the bufmgr to get the next candidate buffer to use in
- *	BufferAlloc(). The only hard requirement BufferAlloc() has is that
- *	this buffer must not currently be pinned. 
- */
-BufferDesc *
-StrategyGetBuffer(void)
-{
-	int				cdb_id;
-	BufferDesc	   *buf;
-
-	if (StrategyControl->listFreeBuffers < 0)
-	{
-		/* We don't have a free buffer, must take one from T1 or T2 */
-
-		if (strategy_get_from == STRAT_LIST_T1)
-		{
-			/*
-			 * We should take the first unpinned buffer from T1.
-			 */
-			cdb_id = StrategyControl->listHead[STRAT_LIST_T1];
-			while (cdb_id >= 0)
-			{
-				buf = &BufferDescriptors[StrategyCDB[cdb_id].buf_id];
-				if (buf->refcount == 0)
-				{
-					strategy_cdb_replace = cdb_id;
-					Assert(StrategyCDB[cdb_id].list == STRAT_LIST_T1);
-					return buf;
-				}
-				cdb_id = StrategyCDB[cdb_id].next;
-			}
-
-			/*
-			 * No unpinned T1 buffer found - pardon T2 cache.
-			 */
-			cdb_id = StrategyControl->listHead[STRAT_LIST_T2];
-			while (cdb_id >= 0)
-			{
-				buf = &BufferDescriptors[StrategyCDB[cdb_id].buf_id];
-				if (buf->refcount == 0)
-				{
-					strategy_cdb_replace = cdb_id;
-					Assert(StrategyCDB[cdb_id].list == STRAT_LIST_T2);
-					return buf;
-				}
-				cdb_id = StrategyCDB[cdb_id].next;
-			}
-
-			/*
-			 * No unpinned buffers at all!!!
-			 */
-			elog(ERROR, "StrategyGetBuffer(): Out of unpinned buffers");
-		}
-		else
-		{
-			/*
-			 * We should take the first unpinned buffer from T2.
-			 */
-			cdb_id = StrategyControl->listHead[STRAT_LIST_T2];
-			while (cdb_id >= 0)
-			{
-				buf = &BufferDescriptors[StrategyCDB[cdb_id].buf_id];
-				if (buf->refcount == 0)
-				{
-					strategy_cdb_replace = cdb_id;
-					Assert(StrategyCDB[cdb_id].list == STRAT_LIST_T2);
-					return buf;
-				}
-				cdb_id = StrategyCDB[cdb_id].next;
-			}
-
-			/*
-			 * No unpinned T2 buffer found - pardon T1 cache.
-			 */
-			cdb_id = StrategyControl->listHead[STRAT_LIST_T1];
-			while (cdb_id >= 0)
-			{
-				buf = &BufferDescriptors[StrategyCDB[cdb_id].buf_id];
-				if (buf->refcount == 0)
-				{
-					strategy_cdb_replace = cdb_id;
-					Assert(StrategyCDB[cdb_id].list == STRAT_LIST_T1);
-					return buf;
-				}
-				cdb_id = StrategyCDB[cdb_id].next;
-			}
-
-			/*
-			 * No unpinned buffers at all!!!
-			 */
-			elog(ERROR, "StrategyGetBuffer(): Out of unpinned buffers");
-		}
-	}
-	else
-	{
-		/* There is a completely free buffer available - take it */
-
-		/*
-		 * Note: This code uses the side effect that a free buffer
-		 * can never be pinned or dirty and therefore the call to
-		 * StrategyReplaceBuffer() will happen without the bufmgr
-		 * releasing the bufmgr-lock in the meantime. That means,
-		 * that there will never be any reason to recheck. Otherwise
-		 * we would leak shared buffers here!
-		 */
-		strategy_cdb_replace = -1;
-		buf = &BufferDescriptors[StrategyControl->listFreeBuffers];
-
-		StrategyControl->listFreeBuffers = buf->bufNext;
-		buf->bufNext = -1;
-
-		/* Buffer of freelist cannot be pinned */
-		Assert(buf->refcount == 0);
-
-		return buf;
-	}
-
-	/* not reached */
-	return NULL;
-}
-
-
-/*
- * StrategyReplaceBuffer
- *
- *	Called by the buffer manager to inform us that he possibly flushed
- * 	a buffer and is now about to replace the content. Prior to this call,
- *	the cache algorithm still reports the buffer as in the cache. After
- *	this call we report the new block, even if IO might still need to
- *	start.
- */
-void
-StrategyReplaceBuffer(BufferDesc *buf, Relation rnode, BlockNumber blockNum)
-{
-	BufferStrategyCDB	   *cdb_found;
-	BufferStrategyCDB	   *cdb_replace;
-
-	if (strategy_cdb_found >= 0)
-	{
-		/* This was a ghost buffer cache hit (B1 or B2) */
-		cdb_found = &StrategyCDB[strategy_cdb_found];
-
-		/* Assert that the buffer remembered in cdb_found is the one */
-		/* the buffer manager is currently faulting in */
-		Assert(BUFFERTAG_EQUALS(&(cdb_found->buf_tag), rnode, blockNum));
-		
-		if (strategy_cdb_replace >= 0)
-		{
-			/* We are satisfying it with an evicted T buffer */
-			cdb_replace = &StrategyCDB[strategy_cdb_replace];
-
-			/* Assert that the buffer remembered in cdb_replace is */
-			/* the one the buffer manager has just evicted */
-			Assert(cdb_replace->list == STRAT_LIST_T1 || 
-					cdb_replace->list == STRAT_LIST_T2);
-			Assert(cdb_replace->buf_id == buf->buf_id);
-			Assert(BUFFERTAGS_EQUAL(&(cdb_replace->buf_tag), &(buf->tag)));
-
-			/* If this was a T1 buffer faulted in by vacuum, just */
-			/* do not cause the CDB end up in the B1 list, so that */
-			/* the vacuum scan does not affect T1_target adjusting */
-			if (strategy_hint_vacuum)
-			{
-				BufTableDelete(&(cdb_replace->buf_tag));
-				STRAT_LIST_REMOVE(cdb_replace);
-				cdb_replace->buf_id = -1;
-				cdb_replace->next = StrategyControl->listUnusedCDB;
-				StrategyControl->listUnusedCDB = strategy_cdb_replace;
-			}
-			else
-			{
-				/* Under normal circumstances move the evicted */
-				/* T list entry to it's corresponding B list */
-				if (cdb_replace->list == STRAT_LIST_T1)
-				{
-					STRAT_LIST_REMOVE(cdb_replace);
-					STRAT_MRU_INSERT(cdb_replace, STRAT_LIST_B1);
-				}
-				else
-				{
-					STRAT_LIST_REMOVE(cdb_replace);
-					STRAT_MRU_INSERT(cdb_replace, STRAT_LIST_B2);
-				}
-			}
-			/* And clear it's block reference */
-			cdb_replace->buf_id = -1;
-		}
-		else
-		{
-			/* or we satisfy it with an unused buffer */
-		}
-
-		/* Now the found B CDB get's the buffer and is moved to T2 */
-		cdb_found->buf_id = buf->buf_id;
-		STRAT_LIST_REMOVE(cdb_found);
-		STRAT_MRU_INSERT(cdb_found, STRAT_LIST_T2);
-	}
-	else
-	{
-		/* This was a complete cache miss, so we need to create */
-		/* a new CDB. The goal is to keep T1len+B1len <= c */
-
-		if (B1_LENGTH > 0 && (T1_LENGTH + B1_LENGTH) >= Data_Descriptors)
-		{
-			/* So if B1 isn't empty and T1len+B1len >= c we take B1-LRU */
-			cdb_found = &StrategyCDB[StrategyControl->listHead[STRAT_LIST_B1]];
-
-			BufTableDelete(&(cdb_found->buf_tag));
-			STRAT_LIST_REMOVE(cdb_found);
-		}
-		else
-		{
-			/* Otherwise, we try to use a free one */
-			if (StrategyControl->listUnusedCDB >= 0)
-			{
-				cdb_found = &StrategyCDB[StrategyControl->listUnusedCDB];
-				StrategyControl->listUnusedCDB = cdb_found->next;
-			}
-			else
-			{
-				/* If there isn't, we take B2-LRU ... except if */
-				/* T1len+B1len+T2len = c ... oh my */
-				if (B2_LENGTH > 0)
-					cdb_found = &StrategyCDB[StrategyControl->listHead[STRAT_LIST_B2]];
-				else
-					cdb_found = &StrategyCDB[StrategyControl->listHead[STRAT_LIST_B1]];
-
-				BufTableDelete(&(cdb_found->buf_tag));
-				STRAT_LIST_REMOVE(cdb_found);
-			}
-		}
-
-		/* Set the CDB's buf_tag and insert the hash key */
-		INIT_BUFFERTAG(&(cdb_found->buf_tag), rnode, blockNum);
-		BufTableInsert(&(cdb_found->buf_tag), (cdb_found - StrategyCDB));
-
-		if (strategy_cdb_replace >= 0)
-		{
-			/* The buffer was formerly in a T list, move it's CDB
-			 * to the corresponding B list */
-			cdb_replace = &StrategyCDB[strategy_cdb_replace];
-
-			Assert(cdb_replace->list == STRAT_LIST_T1 || 
-					cdb_replace->list == STRAT_LIST_T2);
-			Assert(cdb_replace->buf_id == buf->buf_id);
-			Assert(BUFFERTAGS_EQUAL(&(cdb_replace->buf_tag), &(buf->tag)));
-
-			if (cdb_replace->list == STRAT_LIST_T1)
-			{
-				STRAT_LIST_REMOVE(cdb_replace);
-				STRAT_MRU_INSERT(cdb_replace, STRAT_LIST_B1);
-			}
-			else
-			{
-				STRAT_LIST_REMOVE(cdb_replace);
-				STRAT_MRU_INSERT(cdb_replace, STRAT_LIST_B2);
-			}
-			/* And clear it's block reference */
-			cdb_replace->buf_id = -1;
-		}
-		else
-		{
-			/* or we satisfy it with an unused buffer */
-		}
-
-		/* Assign the buffer id to the new CDB */
-		cdb_found->buf_id = buf->buf_id;
-
-		/*
-		 * Specialized VACUUM optimization. If this "complete cache miss"
-		 * happened because vacuum needed the page, we want it later on
-		 * to be placed at the LRU instead of the MRU position of T1.
-		 */
-		if (strategy_hint_vacuum)
-		{
-			if (strategy_vacuum_xid != GetCurrentTransactionId())
-			{
-				strategy_hint_vacuum = false;
-				STRAT_MRU_INSERT(cdb_found, STRAT_LIST_T1);
-			}
-			else
-				STRAT_LRU_INSERT(cdb_found, STRAT_LIST_T1);
-			
-		}
-		else
-			STRAT_MRU_INSERT(cdb_found, STRAT_LIST_T1);
-
-		/*
-		 * Remember the Xid when this buffer went onto T1 to avoid
-		 * a single UPDATE promoting a newcomer straight into T2.
-		 */
-		cdb_found->t1_xid = GetCurrentTransactionId();
-	}
-}
-
-
-/*
- * StrategyInvalidateBuffer
- *
- *	Called by the buffer manager to inform us that a buffer content
- *	is no longer valid. We simply throw away any eventual existing
- *	buffer hash entry and move the CDB and buffer to the free lists.
- */
-void
-StrategyInvalidateBuffer(BufferDesc *buf)
-{
-	int					cdb_id;
-	BufferStrategyCDB  *cdb;
-
-	cdb_id = BufTableLookup(&(buf->tag));
-
-	/* If we have the buffer somewhere in the directory, remove it
-	 * and add the CDB to the list of unused CDB's. */
-	if (cdb_id >= 0)
-	{
-		cdb = &StrategyCDB[cdb_id];
-		BufTableDelete(&(cdb->buf_tag));
-		STRAT_LIST_REMOVE(cdb);
-		cdb->buf_id = -1;
-		cdb->next = StrategyControl->listUnusedCDB;
-		StrategyControl->listUnusedCDB = cdb_id;
-	}
-
-	/* Buffer is unreferenced now and should not contain any valid data
-	 * so add it to the list of free buffers */
-	buf->bufNext = StrategyControl->listFreeBuffers;
-	StrategyControl->listFreeBuffers = buf->buf_id;
-}
-
-
-void
-StrategyHintVacuum(bool vacuum_active)
-{
-	strategy_hint_vacuum = vacuum_active;
-	strategy_vacuum_xid = GetCurrentTransactionId();
-}
-
-
-int
-StrategyDirtyBufferList(int *buffer_list, int max_buffers)
-{
-	int					num_buffer_dirty = 0;
-	int					cdb_id_t1;
-	int					cdb_id_t2;
-	int					buf_id;
-	BufferDesc		   *buf;
-
-	/*
-	 * Traverse the T1 and T2 list LRU to MRU in "parallel"
-	 * and add all dirty buffers found in that order to the list.
-	 * The ARC strategy keeps all used buffers including pinned ones
-	 * in the T1 or T2 list. So we cannot loose any dirty buffers.
-	 */
-	cdb_id_t1 = StrategyControl->listHead[STRAT_LIST_T1];
-	cdb_id_t2 = StrategyControl->listHead[STRAT_LIST_T2];
-
-	while ((cdb_id_t1 >= 0 || cdb_id_t2 >= 0) && 
-			num_buffer_dirty < max_buffers)
-	{
-		if (cdb_id_t1 >= 0)
-		{
-			buf_id = StrategyCDB[cdb_id_t1].buf_id;
-			buf = &BufferDescriptors[buf_id];
-
-			if (buf->flags & BM_VALID)
-			{
-				if ((buf->flags & BM_DIRTY) || (buf->cntxDirty))
-				{
-					buffer_list[num_buffer_dirty++] = buf_id;
-				}
-			}
-
-			cdb_id_t1 = StrategyCDB[cdb_id_t1].next;
-		}
-
-		if (cdb_id_t2 >= 0)
-		{
-			buf_id = StrategyCDB[cdb_id_t2].buf_id;
-			buf = &BufferDescriptors[buf_id];
-
-			if (buf->flags & BM_VALID)
-			{
-				if ((buf->flags & BM_DIRTY) || (buf->cntxDirty))
-				{
-					buffer_list[num_buffer_dirty++] = buf_id;
-				}
-			}
-
-			cdb_id_t2 = StrategyCDB[cdb_id_t2].next;
-		}
-	}
-
-	return num_buffer_dirty;
-}
-
-
-/*
- * StrategyInitialize -- initialize the buffer cache replacement
- *		strategy.
- *
- * Assume: All of the buffers are already building a linked list.
- *		Only called by postmaster and only during initialization.
- */
-void
-StrategyInitialize(bool init)
+static void
+AddBufferToFreelist(BufferDesc *bf)
 {
-	bool found;
-	int i;
-
-	/*
-	 * Initialize the shared CDB lookup hashtable
-	 */
-	InitBufTable(Data_Descriptors * 2);
-
-	/*
-	 * Get or create the shared strategy control block and the CDB's
-	 */
-	StrategyControl = (BufferStrategyControl *)
-			ShmemInitStruct("Buffer Strategy Status",
-					sizeof(BufferStrategyControl) +
-					sizeof(BufferStrategyCDB) * (Data_Descriptors * 2 - 1),
-					&found);
-	StrategyCDB = &(StrategyControl->cdb[0]);
-
-	if (!found)
-	{
-		/*
-		 * Only done once, usually in postmaster
-		 */
-		Assert(init);
-
-		/*
-		 * Grab the whole linked list of free buffers for our
-		 * strategy
-		 */
-		StrategyControl->listFreeBuffers = 0;
-
-		/*
-		 * We start off with a target T1 list size of
-		 * half the available cache blocks.
-		 */
-		StrategyControl->target_T1_size = Data_Descriptors / 2;
-
-		/*
-		 * Initialize B1, T1, T2 and B2 lists to be empty
-		 */
-		for (i = 0; i < STRAT_NUM_LISTS; i++)
-		{
-			StrategyControl->listHead[i] = -1;
-			StrategyControl->listTail[i] = -1;
-			StrategyControl->listSize[i] = 0;
-			StrategyControl->num_hit[i] = 0;
-		}
-		StrategyControl->num_lookup  = 0;
-		StrategyControl->stat_report = 0;
-
-		/*
-		 * All CDB's are linked as the listUnusedCDB
-		 */
-		for (i = 0; i < Data_Descriptors * 2; i++)
-		{
-			StrategyCDB[i].next = i + 1;
-			StrategyCDB[i].list = STRAT_LIST_UNUSED;
-			CLEAR_BUFFERTAG(&(StrategyCDB[i].buf_tag));
-			StrategyCDB[i].buf_id = -1;
-		}
-		StrategyCDB[Data_Descriptors * 2 - 1].next = -1;
-		StrategyControl->listUnusedCDB = 0;
-	}
-	else
-	{
-		Assert(!init);
-	}
+#ifdef BMTRACE
+	_bm_trace(bf->tag.relId.dbId, bf->tag.relId.relId, bf->tag.blockNum,
+			  BufferDescriptorGetBuffer(bf), BMT_DEALLOC);
+#endif   /* BMTRACE */
+	IsNotInQueue(bf);
+
+	/* change bf so it points to inFrontOfNew and its successor */
+	bf->freePrev = SharedFreeList->freePrev;
+	bf->freeNext = Free_List_Descriptor;
+
+	/* insert new into chain */
+	BufferDescriptors[bf->freeNext].freePrev = bf->buf_id;
+	BufferDescriptors[bf->freePrev].freeNext = bf->buf_id;
 }
 
-
 #undef PinBuffer
 
 /*
@@ -853,9 +95,18 @@ PinBuffer(BufferDesc *buf)
 
 	if (buf->refcount == 0)
 	{
+		IsInQueue(buf);
+
+		/* remove from freelist queue */
+		BufferDescriptors[buf->freeNext].freePrev = buf->freePrev;
+		BufferDescriptors[buf->freePrev].freeNext = buf->freeNext;
+		buf->freeNext = buf->freePrev = INVALID_DESCRIPTOR;
+
 		/* mark buffer as no longer free */
 		buf->flags &= ~BM_FREE;
 	}
+	else
+		IsNotInQueue(buf);
 
 	if (PrivateRefCount[b] == 0)
 		buf->refcount++;
@@ -893,6 +144,7 @@ UnpinBuffer(BufferDesc *buf)
 {
 	int			b = BufferDescriptorGetBuffer(buf) - 1;
 
+	IsNotInQueue(buf);
 	Assert(buf->refcount > 0);
 	Assert(PrivateRefCount[b] > 0);
 	PrivateRefCount[b]--;
@@ -902,6 +154,7 @@ UnpinBuffer(BufferDesc *buf)
 	if (buf->refcount == 0)
 	{
 		/* buffer is now unpinned */
+		AddBufferToFreelist(buf);
 		buf->flags |= BM_FREE;
 	}
 	else if ((buf->flags & BM_PIN_COUNT_WAITER) != 0 &&
@@ -934,6 +187,64 @@ refcount = %ld, file: %s, line: %d\n",
 }
 #endif
 
+/*
+ * GetFreeBuffer() -- get the 'next' buffer from the freelist.
+ */
+BufferDesc *
+GetFreeBuffer(void)
+{
+	BufferDesc *buf;
+
+	if (Free_List_Descriptor == SharedFreeList->freeNext)
+	{
+		/* queue is empty. All buffers in the buffer pool are pinned. */
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+				 errmsg("out of free buffers")));
+		return NULL;
+	}
+	buf = &(BufferDescriptors[SharedFreeList->freeNext]);
+
+	/* remove from freelist queue */
+	BufferDescriptors[buf->freeNext].freePrev = buf->freePrev;
+	BufferDescriptors[buf->freePrev].freeNext = buf->freeNext;
+	buf->freeNext = buf->freePrev = INVALID_DESCRIPTOR;
+
+	buf->flags &= ~(BM_FREE);
+
+	return buf;
+}
+
+/*
+ * InitFreeList -- initialize the dummy buffer descriptor used
+ *		as a freelist head.
+ *
+ * Assume: All of the buffers are already linked in a circular
+ *		queue.	 Only called by postmaster and only during
+ *		initialization.
+ */
+void
+InitFreeList(bool init)
+{
+	SharedFreeList = &(BufferDescriptors[Free_List_Descriptor]);
+
+	if (init)
+	{
+		/* we only do this once, normally in the postmaster */
+		SharedFreeList->data = INVALID_OFFSET;
+		SharedFreeList->flags = 0;
+		SharedFreeList->flags &= ~(BM_VALID | BM_DELETED | BM_FREE);
+		SharedFreeList->buf_id = Free_List_Descriptor;
+
+		/* insert it into a random spot in the circular queue */
+		SharedFreeList->freeNext = BufferDescriptors[0].freeNext;
+		SharedFreeList->freePrev = 0;
+		BufferDescriptors[SharedFreeList->freeNext].freePrev =
+			BufferDescriptors[SharedFreeList->freePrev].freeNext =
+			Free_List_Descriptor;
+	}
+}
+
 
 /*
  * print out the free list and check for breaks.
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index ac235ecc3a..3dcb3748dc 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -10,7 +10,7 @@
  * Written by Peter Eisentraut <peter_e@gmx.net>.
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.167 2003/11/13 00:40:01 wieck Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.168 2003/11/13 05:34:58 wieck Exp $
  *
  *--------------------------------------------------------------------
  */
@@ -73,7 +73,6 @@ extern int	CheckPointTimeout;
 extern int	CommitDelay;
 extern int	CommitSiblings;
 extern char *preload_libraries_string;
-extern int	BufferStrategyStatInterval;
 
 #ifdef HAVE_SYSLOG
 extern char *Syslog_facility;
@@ -1191,15 +1190,6 @@ static struct config_int ConfigureNamesInt[] =
 		-1, -1, INT_MAX / 1000, NULL, NULL
 	},
 
-	{
-		{"buffer_strategy_status_interval", PGC_POSTMASTER, RESOURCES_MEM,
-			gettext_noop("Interval to report buffer strategy status in seconds"),
-			NULL
-		},
-		&BufferStrategyStatInterval,
-		0, 0, 600, NULL, NULL
-	},
-
 	/* End-of-list marker */
 	{
 		{NULL, 0, 0, NULL, NULL}, NULL, 0, 0, 0, NULL, NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 15c73e6692..1ead89e130 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -58,7 +58,6 @@
 #shared_buffers = 1000		# min 16, at least max_connections*2, 8KB each
 #sort_mem = 1024		# min 64, size in KB
 #vacuum_mem = 8192		# min 1024, size in KB
-#buffer_strategy_status_interval = 0	# 0-600 seconds
 
 # - Free Space Map -
 
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 492f16cc11..d5b509fe51 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: miscadmin.h,v 1.135 2003/11/13 00:40:01 wieck Exp $
+ * $Id: miscadmin.h,v 1.136 2003/11/13 05:34:58 wieck Exp $
  *
  * NOTES
  *	  some of the information in this file should be moved to
@@ -96,13 +96,6 @@ extern void ProcessInterrupts(void);
 		CritSectionCount--; \
 	} while(0)
 
-#define PG_DELAY(_msec) \
-{ \
-	struct timeval delay; \
-	delay.tv_sec = (_msec) / 1000; \
-	delay.tv_usec = ((_msec) % 1000) * 1000; \
-	(void) select(0, NULL, NULL, NULL, &delay); \
-}
 
 /*****************************************************************************
  *	  globals.h --															 *
diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h
index deafa0b8ce..7b79751339 100644
--- a/src/include/storage/buf_internals.h
+++ b/src/include/storage/buf_internals.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: buf_internals.h,v 1.62 2003/11/13 00:40:02 wieck Exp $
+ * $Id: buf_internals.h,v 1.63 2003/11/13 05:34:58 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -72,29 +72,17 @@ typedef struct buftag
 	(a)->rnode = (xx_reln)->rd_node \
 )
 
-#define BUFFERTAG_EQUALS(a,xx_reln,xx_blockNum) \
-( \
-	(a)->rnode.tblNode == (xx_reln)->rd_node.tblNode && \
-	(a)->rnode.relNode == (xx_reln)->rd_node.relNode && \
-	(a)->blockNum == (xx_blockNum) \
-)
-#define BUFFERTAGS_EQUAL(a,b) \
-( \
-	(a)->rnode.tblNode == (b)->rnode.tblNode && \
-	(a)->rnode.relNode == (b)->rnode.relNode && \
-	(a)->blockNum == (b)->blockNum \
-)
-
 /*
  *	BufferDesc -- shared buffer cache metadata for a single
  *				  shared buffer descriptor.
  */
 typedef struct sbufdesc
 {
-	Buffer		bufNext;		/* link in freelist chain */
+	Buffer		freeNext;		/* links for freelist chain */
+	Buffer		freePrev;
 	SHMEM_OFFSET data;			/* pointer to data in buf pool */
 
-	/* tag and id must be together for table lookup */
+	/* tag and id must be together for table lookup (still true?) */
 	BufferTag	tag;			/* file/block identifier */
 	int			buf_id;			/* buffer's index number (from 0) */
 
@@ -119,7 +107,6 @@ typedef struct sbufdesc
 
 #define BufferDescriptorGetBuffer(bdesc) ((bdesc)->buf_id + 1)
 
-
 /*
  * Each backend has its own BufferLocks[] array holding flag bits
  * showing what locks it has set on each buffer.
@@ -180,19 +167,14 @@ extern long int LocalBufferFlushCount;
 /*freelist.c*/
 extern void PinBuffer(BufferDesc *buf);
 extern void UnpinBuffer(BufferDesc *buf);
-extern BufferDesc *StrategyBufferLookup(BufferTag *tagPtr, bool recheck);
-extern BufferDesc *StrategyGetBuffer(void);
-extern void StrategyReplaceBuffer(BufferDesc *buf, Relation rnode, BlockNumber blockNum);
-extern void StrategyInvalidateBuffer(BufferDesc *buf);
-extern void StrategyHintVacuum(bool vacuum_active);
-extern int StrategyDirtyBufferList(int *buffer_dirty, int max_buffers);
-extern void StrategyInitialize(bool init);
+extern BufferDesc *GetFreeBuffer(void);
+extern void InitFreeList(bool init);
 
 /* buf_table.c */
-extern void InitBufTable(int size);
-extern int BufTableLookup(BufferTag *tagPtr);
-extern bool BufTableInsert(BufferTag *tagPtr, Buffer buf_id);
-extern bool BufTableDelete(BufferTag *tagPtr);
+extern void InitBufTable(void);
+extern BufferDesc *BufTableLookup(BufferTag *tagPtr);
+extern bool BufTableDelete(BufferDesc *buf);
+extern bool BufTableInsert(BufferDesc *buf);
 
 /* bufmgr.c */
 extern BufferDesc *BufferDescriptors;