Remove the separate 'stats buffer' process, letting backend stats messages

be delivered directly to the collector process.  The extra process context
swaps required to transfer data through the buffer process seem to outweigh
any value the buffering might have.  Per recent discussion and tests.
I modified Bruce's draft patch to use poll() rather than select() where
available (this makes a noticeable difference on my system), and fixed
up the EXEC_BACKEND case.

doc/src/sgml/monitoring.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/monitoring.sgml,v 1.35 2006/06/27 19:07:50 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/monitoring.sgml,v 1.36 2006/06/29 20:00:08 tgl Exp $ -->
 
 <chapter id="monitoring">
  <title>Monitoring Database Activity</title>
@@ -50,7 +50,7 @@
 <screen>
 $ ps auxww | grep ^postgres
 postgres   960  0.0  1.1  6104 1480 pts/1    SN   13:17   0:00 postgres -i
-postgres   963  0.0  1.1  7084 1472 pts/1    SN   13:17   0:00 postgres: stats buffer process   
+postgres   963  0.0  1.1  7084 1472 pts/1    SN   13:17   0:00 postgres: writer process
 postgres   965  0.0  1.1  6152 1512 pts/1    SN   13:17   0:00 postgres: stats collector process   
 postgres   998  0.0  2.3  6532 2992 pts/1    SN   13:18   0:00 postgres: tgl runbug 127.0.0.1 idle
 postgres  1003  0.0  2.4  6532 3128 pts/1    SN   13:19   0:00 postgres: tgl regression [local] SELECT waiting
@@ -60,10 +60,11 @@ postgres  1016  0.1  2.4  6532 3080 pts/1    SN   13:19   0:00 postgres: tgl reg
    (The appropriate invocation of <command>ps</> varies across different
    platforms, as do the details of what is shown.  This example is from a
    recent Linux system.)  The first process listed here is the
-   the master server process.  The command arguments
+   master server process.  The command arguments
    shown for it are the same ones given when it was launched.  The next two
-   processes implement the statistics collector, which will be described in
-   detail in the next section.  (These will not be present if you have set
+   processes are background worker processes automatically launched by the
+   master process.  (The <quote>stats collector</> process will not be present
+   if you have set
    the system not to start the statistics collector.)  Each of the remaining
    processes is a server process handling one client connection.  Each such
    process sets its command line display in the form
@@ -83,6 +84,13 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
   thereby release some lock or other.
   </para>
 
+  <para>
+   If you have turned off <xref linkend="guc-update-process-title"> then the
+   activity indicator is not updated; the process title is set only once
+   when a new process is launched.  On some platforms this saves a useful
+   amount of per-command overhead, on others it's insignificant.
+  </para>
+
   <tip>
   <para>
   <productname>Solaris</productname> requires special handling. You must

src/backend/postmaster/postmaster.c

@@ -37,7 +37,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.489 2006/06/27 22:16:43 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.490 2006/06/29 20:00:08 tgl Exp $
  *
  * NOTES
  *
@@ -331,8 +331,6 @@ typedef struct
 	PROC_HDR   *ProcGlobal;
 	PGPROC	   *DummyProcs;
 	InheritableSocket pgStatSock;
-	InheritableSocket pgStatPipe0;
-	InheritableSocket pgStatPipe1;
 	pid_t		PostmasterPid;
 	TimestampTz PgStartTime;
 #ifdef WIN32
@@ -2352,7 +2350,7 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)
 		kill(PgArchPID, SIGQUIT);
 	}
 
-	/* Force a power-cycle of the pgstat processes too */
+	/* Force a power-cycle of the pgstat process too */
 	/* (Shouldn't be necessary, but just for luck) */
 	if (PgStatPID != 0 && !FatalError)
 	{
@@ -3324,25 +3322,13 @@ SubPostmasterMain(int argc, char *argv[])
 		PgArchiverMain(argc, argv);
 		proc_exit(0);
 	}
-	if (strcmp(argv[1], "--forkbuf") == 0)
+	if (strcmp(argv[1], "--forkcol") == 0)
 	{
 		/* Close the postmaster's sockets */
 		ClosePostmasterPorts(false);
 
 		/* Do not want to attach to shared memory */
 
-		PgstatBufferMain(argc, argv);
-		proc_exit(0);
-	}
-	if (strcmp(argv[1], "--forkcol") == 0)
-	{
-		/*
-		 * Do NOT close postmaster sockets here, because we are forking from
-		 * pgstat buffer process, which already did it.
-		 */
-
-		/* Do not want to attach to shared memory */
-
 		PgstatCollectorMain(argc, argv);
 		proc_exit(0);
 	}
@@ -3679,7 +3665,6 @@ extern slock_t *ProcStructLock;
 extern PROC_HDR *ProcGlobal;
 extern PGPROC *DummyProcs;
 extern int	pgStatSock;
-extern int	pgStatPipe[2];
 
 #ifndef WIN32
 #define write_inheritable_socket(dest, src, childpid) (*(dest) = (src))
@@ -3723,8 +3708,6 @@ save_backend_variables(BackendParameters * param, Port *port,
 	param->ProcGlobal = ProcGlobal;
 	param->DummyProcs = DummyProcs;
 	write_inheritable_socket(&param->pgStatSock, pgStatSock, childPid);
-	write_inheritable_socket(&param->pgStatPipe0, pgStatPipe[0], childPid);
-	write_inheritable_socket(&param->pgStatPipe1, pgStatPipe[1], childPid);
 
 	param->PostmasterPid = PostmasterPid;
 	param->PgStartTime = PgStartTime;
@@ -3928,8 +3911,6 @@ restore_backend_variables(BackendParameters * param, Port *port)
 	ProcGlobal = param->ProcGlobal;
 	DummyProcs = param->DummyProcs;
 	read_inheritable_socket(&pgStatSock, &param->pgStatSock);
-	read_inheritable_socket(&pgStatPipe[0], &param->pgStatPipe0);
-	read_inheritable_socket(&pgStatPipe[1], &param->pgStatPipe1);
 
 	PostmasterPid = param->PostmasterPid;
 	PgStartTime = param->PgStartTime;

src/include/pgstat.h

@@ -5,7 +5,7 @@
  *
  *	Copyright (c) 2001-2006, PostgreSQL Global Development Group
  *
- *	$PostgreSQL: pgsql/src/include/pgstat.h,v 1.47 2006/06/19 01:51:21 tgl Exp $
+ *	$PostgreSQL: pgsql/src/include/pgstat.h,v 1.48 2006/06/29 20:00:08 tgl Exp $
  * ----------
  */
 #ifndef PGSTAT_H
@@ -362,7 +362,6 @@ extern int	pgstat_start(void);
 extern void pgstat_reset_all(void);
 
 #ifdef EXEC_BACKEND
-extern void PgstatBufferMain(int argc, char *argv[]);
 extern void PgstatCollectorMain(int argc, char *argv[]);
 #endif