Move each SLRU's lwlocks to a separate tranche.

This makes it significantly easier to identify these lwlocks in
LWLOCK_STATS or Trace_lwlocks output.  It's also arguably better
from a modularity standpoint, since lwlock.c no longer needs to
know anything about the LWLock needs of the higher-level SLRU
facility.

Ildus Kurbangaliev, reviewd by Álvaro Herrera and by me.

src/backend/storage/lmgr/lwlock.c

@@ -76,11 +76,6 @@
  */
 #include "postgres.h"
 
-#include "access/clog.h"
-#include "access/commit_ts.h"
-#include "access/multixact.h"
-#include "access/subtrans.h"
-#include "commands/async.h"
 #include "miscadmin.h"
 #include "pg_trace.h"
 #include "postmaster/postmaster.h"
@@ -364,24 +359,6 @@ NumLWLocks(void)
 	/* proc.c needs one for each backend or auxiliary process */
 	numLocks += MaxBackends + NUM_AUXILIARY_PROCS;
 
-	/* clog.c needs one per CLOG buffer */
-	numLocks += CLOGShmemBuffers();
-
-	/* commit_ts.c needs one per CommitTs buffer */
-	numLocks += CommitTsShmemBuffers();
-
-	/* subtrans.c needs one per SubTrans buffer */
-	numLocks += NUM_SUBTRANS_BUFFERS;
-
-	/* multixact.c needs two SLRU areas */
-	numLocks += NUM_MXACTOFFSET_BUFFERS + NUM_MXACTMEMBER_BUFFERS;
-
-	/* async.c needs one per Async buffer */
-	numLocks += NUM_ASYNC_BUFFERS;
-
-	/* predicate.c needs one per old serializable xid buffer */
-	numLocks += NUM_OLDSERXID_BUFFERS;
-
 	/* slot.c needs one for each slot */
 	numLocks += max_replication_slots;
 

src/backend/storage/lmgr/predicate.c

@@ -794,7 +794,7 @@ OldSerXidInit(void)
 	 * Set up SLRU management of the pg_serial data.
 	 */
 	OldSerXidSlruCtl->PagePrecedes = OldSerXidPagePrecedesLogically;
-	SimpleLruInit(OldSerXidSlruCtl, "OldSerXid SLRU Ctl",
+	SimpleLruInit(OldSerXidSlruCtl, "oldserxid",
 				  NUM_OLDSERXID_BUFFERS, 0, OldSerXidLock, "pg_serial");
 	/* Override default assumption that writes should be fsync'd */
 	OldSerXidSlruCtl->do_fsync = false;