Split the shared-memory array of PGPROC pointers out of the sinval

communication structure, and make it its own module with its own lock.
This should reduce contention at least a little, and it definitely makes
the code seem cleaner.  Per my recent proposal.

src/include/storage/buf_internals.h

@@ -8,14 +8,13 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/buf_internals.h,v 1.77 2005/03/04 20:21:07 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/storage/buf_internals.h,v 1.78 2005/05/19 21:35:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #ifndef BUFMGR_INTERNALS_H
 #define BUFMGR_INTERNALS_H
 
-#include "storage/backendid.h"
 #include "storage/buf.h"
 #include "storage/lwlock.h"
 #include "storage/shmem.h"
@@ -94,7 +93,7 @@ typedef struct buftag
  *	BufferDesc -- shared descriptor/state data for a single shared buffer.
  *
  * Note: buf_hdr_lock must be held to examine or change the tag, flags,
- * usage_count, refcount, or wait_backend_id fields.  buf_id field never
+ * usage_count, refcount, or wait_backend_pid fields.  buf_id field never
  * changes after initialization, so does not need locking.  freeNext is
  * protected by the BufFreelistLock not buf_hdr_lock.  The LWLocks can take
  * care of themselves.  The buf_hdr_lock is *not* used to control access to
@@ -108,8 +107,8 @@ typedef struct buftag
  *
  * We can't physically remove items from a disk page if another backend has
  * the buffer pinned.  Hence, a backend may need to wait for all other pins
- * to go away.  This is signaled by storing its own backend ID into
- * wait_backend_id and setting flag bit BM_PIN_COUNT_WAITER.  At present,
+ * to go away.  This is signaled by storing its own PID into
+ * wait_backend_pid and setting flag bit BM_PIN_COUNT_WAITER.  At present,
  * there can be only one such waiter per buffer.
  *
  * We use this same struct for local buffer headers, but the lock fields
@@ -121,7 +120,7 @@ typedef struct sbufdesc
 	BufFlags	flags;			/* see bit definitions above */
 	uint16		usage_count;	/* usage counter for clock sweep code */
 	unsigned	refcount;		/* # of backends holding pins on buffer */
-	BackendId	wait_backend_id;	/* backend ID of pin-count waiter */
+	int			wait_backend_pid; /* backend PID of pin-count waiter */
 
 	slock_t		buf_hdr_lock;	/* protects the above fields */
 

src/include/storage/lwlock.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/lwlock.h,v 1.18 2005/04/28 21:47:18 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/storage/lwlock.h,v 1.19 2005/05/19 21:35:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -30,6 +30,7 @@ typedef enum LWLockId
 	LockMgrLock,
 	OidGenLock,
 	XidGenLock,
+	ProcArrayLock,
 	SInvalLock,
 	FreeSpaceLock,
 	MMCacheLock,

src/include/storage/proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.77 2004/12/31 22:03:42 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.78 2005/05/19 21:35:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -15,7 +15,6 @@
 #define _PROC_H_
 
 #include "access/xlog.h"
-#include "storage/backendid.h"
 #include "storage/lock.h"
 #include "storage/pg_sema.h"
 
@@ -137,7 +136,7 @@ extern bool LockWaitCancel(void);
 
 extern void ProcWaitForSignal(void);
 extern void ProcCancelWaitForSignal(void);
-extern void ProcSendSignal(BackendId procId);
+extern void ProcSendSignal(int pid);
 
 extern bool enable_sig_alarm(int delayms, bool is_statement_timeout);
 extern bool disable_sig_alarm(bool is_statement_timeout);

src/include/storage/procarray.h

@@ -0,0 +1,36 @@
+/*-------------------------------------------------------------------------
+ *
+ * procarray.h
+ *	  POSTGRES process array definitions.
+ *
+ *
+ * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.1 2005/05/19 21:35:47 tgl Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PROCARRAY_H
+#define PROCARRAY_H
+
+extern int	ProcArrayShmemSize(int maxBackends);
+extern void CreateSharedProcArray(int maxBackends);
+extern void ProcArrayAddMyself(void);
+extern void ProcArrayRemoveMyself(void);
+
+extern bool TransactionIdIsInProgress(TransactionId xid);
+extern TransactionId GetOldestXmin(bool allDbs);
+
+/* Use "struct PGPROC", not PGPROC, to avoid including proc.h here */
+extern struct PGPROC *BackendPidGetProc(int pid);
+extern bool IsBackendPid(int pid);
+extern bool DatabaseHasActiveBackends(Oid databaseId, bool ignoreMyself);
+
+extern int	CountActiveBackends(void);
+extern int	CountEmptyBackendSlots(void);
+
+extern void XidCacheRemoveRunningXids(TransactionId xid,
+						  int nxids, TransactionId *xids);
+
+#endif   /* PROCARRAY_H */

src/include/storage/sinval.h

@@ -7,14 +7,13 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/sinval.h,v 1.40 2005/01/10 21:57:19 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/storage/sinval.h,v 1.41 2005/05/19 21:35:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #ifndef SINVAL_H
 #define SINVAL_H
 
-#include "storage/backendid.h"
 #include "storage/itemptr.h"
 #include "storage/relfilenode.h"
 
@@ -87,24 +86,12 @@ typedef union
 extern int	SInvalShmemSize(int maxBackends);
 extern void CreateSharedInvalidationState(int maxBackends);
 extern void InitBackendSharedInvalidationState(void);
+
 extern void SendSharedInvalidMessage(SharedInvalidationMessage *msg);
 extern void ReceiveSharedInvalidMessages(
 				  void (*invalFunction) (SharedInvalidationMessage *msg),
 							 void (*resetFunction) (void));
 
-extern bool DatabaseHasActiveBackends(Oid databaseId, bool ignoreMyself);
-extern bool TransactionIdIsInProgress(TransactionId xid);
-extern bool IsBackendPid(int pid);
-extern TransactionId GetOldestXmin(bool allDbs);
-extern int	CountActiveBackends(void);
-extern int	CountEmptyBackendSlots(void);
-
-/* Use "struct PGPROC", not PGPROC, to avoid including proc.h here */
-extern struct PGPROC *BackendIdGetProc(BackendId procId);
-
-extern void XidCacheRemoveRunningXids(TransactionId xid,
-						  int nxids, TransactionId *xids);
-
 /* signal handler for catchup events (SIGUSR1) */
 extern void CatchupInterruptHandler(SIGNAL_ARGS);
 

src/include/storage/sinvaladt.h

@@ -7,16 +7,16 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/sinvaladt.h,v 1.37 2004/12/31 22:03:42 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/storage/sinvaladt.h,v 1.38 2005/05/19 21:35:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #ifndef SINVALADT_H
 #define SINVALADT_H
 
-#include "storage/shmem.h"
 #include "storage/sinval.h"
 
+
 /*
  * The shared cache invalidation manager is responsible for transmitting
  * invalidation messages between backends.	Any message sent by any backend
@@ -71,7 +71,6 @@ typedef struct ProcState
 	/* nextMsgNum is -1 in an inactive ProcState array entry. */
 	int			nextMsgNum;		/* next message number to read, or -1 */
 	bool		resetState;		/* true, if backend has to reset its state */
-	SHMEM_OFFSET procStruct;	/* location of backend's PGPROC struct */
 } ProcState;
 
 /* Shared cache invalidation memory segment */