Replacement of the buffer replacement strategy with an ARC

algorithm adopted for PostgreSQL.

Jan

Author: Jan Wieck

src/backend/commands/vacuum.c

@@ -13,7 +13,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.265 2003/11/12 21:15:51 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.266 2003/11/13 00:40:00 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -33,6 +33,7 @@
 #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"
@@ -310,8 +311,16 @@ 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
@@ -749,6 +758,12 @@ 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.
@@ -763,6 +778,7 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
 							  ObjectIdGetDatum(relid),
 							  0, 0, 0))
 	{
+		StrategyHintVacuum(false);
 		CommitTransactionCommand();
 		return true;			/* okay 'cause no data there */
 	}
@@ -796,6 +812,7 @@ 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;
 	}
@@ -810,6 +827,7 @@ 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;
 	}
@@ -824,6 +842,7 @@ 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 */
@@ -863,6 +882,7 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
 	/*
 	 * Complete the transaction and free all temporary memory used.
 	 */
+	StrategyHintVacuum(false);
 	CommitTransactionCommand();
 
 	/*

src/backend/storage/buffer/buf_init.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_init.c,v 1.54 2003/08/04 02:40:03 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_init.c,v 1.55 2003/11/13 00:40:01 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -48,9 +48,6 @@ long	   *CurTraceBuf;
 int			ShowPinTrace = 0;
 
 int			Data_Descriptors;
-int			Free_List_Descriptor;
-int			Lookup_List_Descriptor;
-int			Num_Descriptors;
 
 BufferDesc *BufferDescriptors;
 Block	   *BufferBlockPointers;
@@ -133,9 +130,6 @@ 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
@@ -156,7 +150,7 @@ InitBufferPool(void)
 
 	BufferDescriptors = (BufferDesc *)
 		ShmemInitStruct("Buffer Descriptors",
-					  Num_Descriptors * sizeof(BufferDesc), &foundDescs);
+					  Data_Descriptors * sizeof(BufferDesc), &foundDescs);
 
 	BufferBlocks = (char *)
 		ShmemInitStruct("Buffer Blocks",
@@ -176,16 +170,14 @@ InitBufferPool(void)
 		block = BufferBlocks;
 
 		/*
-		 * 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.
+		 * link the buffers into a single linked list. This will become the
+		 * LiFo list of unused buffers returned by StragegyGetBuffer().
 		 */
 		for (i = 0; i < Data_Descriptors; block += BLCKSZ, buf++, i++)
 		{
 			Assert(ShmemIsValid((unsigned long) block));
 
-			buf->freeNext = i + 1;
-			buf->freePrev = i - 1;
+			buf->bufNext = i + 1;
 
 			CLEAR_BUFFERTAG(&(buf->tag));
 			buf->buf_id = i;
@@ -199,14 +191,12 @@ InitBufferPool(void)
 			buf->wait_backend_id = 0;
 		}
 
-		/* close the circular queue */
-		BufferDescriptors[0].freePrev = Data_Descriptors - 1;
-		BufferDescriptors[Data_Descriptors - 1].freeNext = 0;
+		/* Correct last entry */
+		BufferDescriptors[Data_Descriptors - 1].bufNext = -1;
 	}
 
 	/* Init other shared buffer-management stuff */
-	InitBufTable();
-	InitFreeList(!foundDescs);
+	StrategyInitialize(!foundDescs);
 
 	LWLockRelease(BufMgrLock);
 }

src/backend/storage/buffer/buf_table.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_table.c,v 1.29 2003/08/04 02:40:03 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/buf_table.c,v 1.30 2003/11/13 00:40:01 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -38,7 +38,7 @@ static HTAB *SharedBufHash;
  * Initialize shmem hash table for mapping buffers
  */
 void
-InitBufTable(void)
+InitBufTable(int size)
 {
 	HASHCTL		info;
 
@@ -50,87 +50,71 @@ InitBufTable(void)
 	info.hash = tag_hash;
 
 	SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table",
-								  NBuffers, NBuffers,
+								  size, size,
 								  &info,
 								  HASH_ELEM | HASH_FUNCTION);
 
 	if (!SharedBufHash)
 		elog(FATAL, "could not initialize shared buffer hash table");
 }
 
-BufferDesc *
+/*
+ * BufTableLookup
+ */
+int
 BufTableLookup(BufferTag *tagPtr)
 {
 	BufferLookupEnt *result;
 
 	if (tagPtr->blockNum == P_NEW)
-		return NULL;
+		return -1;
 
 	result = (BufferLookupEnt *)
 		hash_search(SharedBufHash, (void *) tagPtr, HASH_FIND, NULL);
 	if (!result)
-		return NULL;
+		return -1;
 
-	return &(BufferDescriptors[result->id]);
+	return result->id;
 }
 
 /*
  * BufTableDelete
  */
 bool
-BufTableDelete(BufferDesc *buf)
+BufTableInsert(BufferTag *tagPtr, Buffer buf_id)
 {
 	BufferLookupEnt *result;
-
-	/*
-	 * 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;
-
-	buf->flags |= BM_DELETED;
+	bool		found;
 
 	result = (BufferLookupEnt *)
-		hash_search(SharedBufHash, (void *) &(buf->tag), HASH_REMOVE, NULL);
+		hash_search(SharedBufHash, (void *) tagPtr, HASH_ENTER, &found);
 
-	if (!result)				/* shouldn't happen */
-		elog(ERROR, "shared buffer hash table corrupted");
+	if (!result)
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of shared memory")));
 
-	/*
-	 * 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;
+	if (found)					/* found something else in the table? */
+		elog(ERROR, "shared buffer hash table corrupted");
 
+	result->id = buf_id;
 	return TRUE;
 }
 
+/*
+ * BufTableDelete
+ */
 bool
-BufTableInsert(BufferDesc *buf)
+BufTableDelete(BufferTag *tagPtr)
 {
 	BufferLookupEnt *result;
-	bool		found;
-
-	/* cannot insert it twice */
-	Assert(buf->flags & BM_DELETED);
-	buf->flags &= ~(BM_DELETED);
 
 	result = (BufferLookupEnt *)
-		hash_search(SharedBufHash, (void *) &(buf->tag), HASH_ENTER, &found);
-
-	if (!result)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of shared memory")));
+		hash_search(SharedBufHash, (void *) tagPtr, HASH_REMOVE, NULL);
 
-	if (found)					/* found something else in the table? */
+	if (!result)				/* shouldn't happen */
 		elog(ERROR, "shared buffer hash table corrupted");
 
-	result->id = buf->buf_id;
 	return TRUE;
 }