Rename dtrace probes for ongoing xlog -> wal conversion.

xlog-switch becomes wal-switch, and xlog-insert becomes wal-insert.

doc/src/sgml/monitoring.sgml

@@ -3349,14 +3349,14 @@ SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
      <entry>Probe that fires when a dirty WAL buffer write is complete.</entry>
     </row>
     <row>
-     <entry><literal>xlog-insert</literal></entry>
+     <entry><literal>wal-insert</literal></entry>
      <entry><literal>(unsigned char, unsigned char)</literal></entry>
      <entry>Probe that fires when a WAL record is inserted.
       arg0 is the resource manager (rmid) for the record.
       arg1 contains the info flags.</entry>
     </row>
     <row>
-     <entry><literal>xlog-switch</literal></entry>
+     <entry><literal>wal-switch</literal></entry>
      <entry><literal>()</literal></entry>
      <entry>Probe that fires when a WAL segment switch is requested.</entry>
     </row>

src/backend/access/transam/xlog.c

@@ -1114,7 +1114,7 @@ XLogInsertRecord(XLogRecData *rdata,
 	 */
 	if (isLogSwitch)
 	{
-		TRACE_POSTGRESQL_XLOG_SWITCH();
+		TRACE_POSTGRESQL_WAL_SWITCH();
 		XLogFlush(EndPos);
 
 		/*

src/backend/access/transam/xloginsert.c

@@ -429,7 +429,7 @@ XLogInsert(RmgrId rmid, uint8 info)
 				  XLR_CHECK_CONSISTENCY)) != 0)
 		elog(PANIC, "invalid xlog info mask %02X", info);
 
-	TRACE_POSTGRESQL_XLOG_INSERT(rmid, info);
+	TRACE_POSTGRESQL_WAL_INSERT(rmid, info);
 
 	/*
 	 * In bootstrap mode, we don't actually log anything but XLOG resources;

src/backend/utils/probes.d

@@ -87,8 +87,8 @@ provider postgresql {
 	probe smgr__md__write__start(ForkNumber, BlockNumber, Oid, Oid, Oid, int);
 	probe smgr__md__write__done(ForkNumber, BlockNumber, Oid, Oid, Oid, int, int, int);
 
-	probe xlog__insert(unsigned char, unsigned char);
-	probe xlog__switch();
+	probe wal__insert(unsigned char, unsigned char);
+	probe wal__switch();
 	probe wal__buffer__write__dirty__start();
 	probe wal__buffer__write__dirty__done();
 };