3 files changed, 37 insertions, 18 deletions
diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h
index 4effa0d740f..18239176b8e 100644
--- a/src/include/storage/buf_internals.h
+++ b/src/include/storage/buf_internals.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/buf_internals.h,v 1.86 2006/03/31 23:32:07 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/storage/buf_internals.h,v 1.87 2006/07/23 03:07:58 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -87,6 +87,17 @@ typedef struct buftag
 )
 
 /*
+ * The shared buffer mapping table is partitioned to reduce contention.
+ * To determine which partition lock a given tag requires, compute the tag's
+ * hash code with BufTableHashCode(), then apply BufMappingPartitionLock().
+ * NB: NUM_BUFFER_PARTITIONS must be a power of 2!
+ */
+#define BufTableHashPartition(hashcode) \
+	((hashcode) % NUM_BUFFER_PARTITIONS)
+#define BufMappingPartitionLock(hashcode) \
+	((LWLockId) (FirstBufMappingLock + BufTableHashPartition(hashcode)))
+
+/*
  *	BufferDesc -- shared descriptor/state data for a single shared buffer.
  *
  * Note: buf_hdr_lock must be held to examine or change the tag, flags,
@@ -182,9 +193,10 @@ extern void StrategyInitialize(bool init);
 /* buf_table.c */
 extern Size BufTableShmemSize(int size);
 extern void InitBufTable(int size);
-extern int	BufTableLookup(BufferTag *tagPtr);
-extern int	BufTableInsert(BufferTag *tagPtr, int buf_id);
-extern void BufTableDelete(BufferTag *tagPtr);
+extern uint32 BufTableHashCode(BufferTag *tagPtr);
+extern int	BufTableLookup(BufferTag *tagPtr, uint32 hashcode);
+extern int	BufTableInsert(BufferTag *tagPtr, uint32 hashcode, int buf_id);
+extern void BufTableDelete(BufferTag *tagPtr, uint32 hashcode);
 
 /* localbuf.c */
 extern BufferDesc *LocalBufferAlloc(Relation reln, BlockNumber blockNum,
diff --git a/src/include/storage/lock.h b/src/include/storage/lock.h
index 136299c060d..d471293b702 100644
--- a/src/include/storage/lock.h
+++ b/src/include/storage/lock.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/lock.h,v 1.94 2006/03/05 15:58:59 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/lock.h,v 1.95 2006/07/23 03:07:58 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -19,23 +19,15 @@
 #include "storage/shmem.h"
 
 
-/*
- * Number of partitions the shared lock tables are divided into.
- *
- * See LockTagToPartition() if you change this.
- */
-#define NUM_LOCK_PARTITIONS  16
+/* struct PGPROC is declared in proc.h, but must forward-reference it */
+typedef struct PGPROC PGPROC;
 
-/* originally in procq.h */
 typedef struct PROC_QUEUE
 {
 	SHM_QUEUE	links;			/* head of list of PGPROC objects */
 	int			size;			/* number of entries in list */
 } PROC_QUEUE;
 
-/* struct PGPROC is declared in proc.h, but must forward-reference it */
-typedef struct PGPROC PGPROC;
-
 /* GUC variables */
 extern int	max_locks_per_xact;
 
diff --git a/src/include/storage/lwlock.h b/src/include/storage/lwlock.h
index 47742c02c59..2810326597e 100644
--- a/src/include/storage/lwlock.h
+++ b/src/include/storage/lwlock.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/lwlock.h,v 1.28 2006/05/08 00:00:17 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/storage/lwlock.h,v 1.29 2006/07/23 03:07:58 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -15,6 +15,18 @@
 #define LWLOCK_H
 
 /*
+ * It's a bit odd to declare NUM_BUFFER_PARTITIONS and NUM_LOCK_PARTITIONS
+ * here, but we need them to set up enum LWLockId correctly, and having
+ * this file include lock.h or bufmgr.h would be backwards.
+ */
+
+/* Number of partitions of the shared buffer mapping hashtable */
+#define NUM_BUFFER_PARTITIONS  16
+
+/* Number of partitions the shared lock tables are divided into */
+#define NUM_LOCK_PARTITIONS  16
+
+/*
  * We have a number of predefined LWLocks, plus a bunch of LWLocks that are
  * dynamically assigned (e.g., for shared buffers).  The LWLock structures
  * live in shared memory (since they contain shared data) and are identified
@@ -25,7 +37,6 @@
  */
 typedef enum LWLockId
 {
-	BufMappingLock,
 	BufFreelistLock,
 	ShmemIndexLock,
 	OidGenLock,
@@ -48,7 +59,11 @@ typedef enum LWLockId
 	TwoPhaseStateLock,
 	TablespaceCreateLock,
 	BtreeVacuumLock,
-	FirstLockMgrLock,			/* must be last except for MaxDynamicLWLock */
+	FirstBufMappingLock,
+	FirstLockMgrLock = FirstBufMappingLock + NUM_BUFFER_PARTITIONS,
+
+	/* must be last except for MaxDynamicLWLock: */
+	NumFixedLWLocks = FirstLockMgrLock + NUM_LOCK_PARTITIONS,
 
 	MaxDynamicLWLock = 1000000000
 } LWLockId;