Implement new 'lightweight lock manager' that's intermediate between

existing lock manager and spinlocks: it understands exclusive vs shared
lock but has few other fancy features.  Replace most uses of spinlocks
with lightweight locks.  All remaining uses of spinlocks have very short
lock hold times (a few dozen instructions), so tweak spinlock backoff
code to work efficiently given this assumption.  All per my proposal on
pghackers 26-Sep-01.

1 files changed, 15 insertions, 17 deletions

diff --git a/src/backend/storage/freespace/freespace.c b/src/backend/storage/freespace/freespace.c
index fec9f594a61..b20e8086157 100644
--- a/src/backend/storage/freespace/freespace.c
+++ b/src/backend/storage/freespace/freespace.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/freespace/freespace.c,v 1.4 2001/07/19 21:25:37 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/freespace/freespace.c,v 1.5 2001/09/29 04:02:23 tgl Exp $
  *
  *
  * NOTES:
@@ -56,6 +56,7 @@
 
 #include "storage/freespace.h"
 #include "storage/itemid.h"
+#include "storage/lwlock.h"
 #include "storage/shmem.h"
 
 
@@ -122,9 +123,6 @@ struct FSMChunk
 };
 
 
-SPINLOCK	FreeSpaceLock;		/* in Shmem or created in
-								 * CreateSpinlocks() */
-
 int		MaxFSMRelations;		/* these are set by guc.c */
 int		MaxFSMPages;
 
@@ -256,7 +254,7 @@ GetPageWithFreeSpace(RelFileNode *rel, Size spaceNeeded)
 	FSMRelation *fsmrel;
 	BlockNumber	freepage;
 
-	SpinAcquire(FreeSpaceLock);
+	LWLockAcquire(FreeSpaceLock, LW_EXCLUSIVE);
 	/*
 	 * We always add a rel to the hashtable when it is inquired about.
 	 */
@@ -279,7 +277,7 @@ GetPageWithFreeSpace(RelFileNode *rel, Size spaceNeeded)
 		fsmrel->threshold = (Size) cur_avg;
 	}
 	freepage = find_free_space(fsmrel, spaceNeeded);
-	SpinRelease(FreeSpaceLock);
+	LWLockRelease(FreeSpaceLock);
 	return freepage;
 }
 
@@ -299,7 +297,7 @@ RecordFreeSpace(RelFileNode *rel, BlockNumber page, Size spaceAvail)
 	/* Sanity check: ensure spaceAvail will fit into ItemLength */
 	AssertArg(spaceAvail < BLCKSZ);
 
-	SpinAcquire(FreeSpaceLock);
+	LWLockAcquire(FreeSpaceLock, LW_EXCLUSIVE);
 	/*
 	 * We choose not to add rels to the hashtable unless they've been
 	 * inquired about with GetPageWithFreeSpace.  Also, a Record operation
@@ -308,11 +306,11 @@ RecordFreeSpace(RelFileNode *rel, BlockNumber page, Size spaceAvail)
 	fsmrel = lookup_fsm_rel(rel);
 	if (fsmrel)
 		fsm_record_free_space(fsmrel, page, spaceAvail);
-	SpinRelease(FreeSpaceLock);
+	LWLockRelease(FreeSpaceLock);
 }
 
 /*
- * RecordAndGetPageWithFreeSpace - combo form to save one spinlock and
+ * RecordAndGetPageWithFreeSpace - combo form to save one lock and
  *		hash table lookup cycle.
  */
 BlockNumber
@@ -327,7 +325,7 @@ RecordAndGetPageWithFreeSpace(RelFileNode *rel,
 	/* Sanity check: ensure spaceAvail will fit into ItemLength */
 	AssertArg(oldSpaceAvail < BLCKSZ);
 
-	SpinAcquire(FreeSpaceLock);
+	LWLockAcquire(FreeSpaceLock, LW_EXCLUSIVE);
 	/*
 	 * We always add a rel to the hashtable when it is inquired about.
 	 */
@@ -351,7 +349,7 @@ RecordAndGetPageWithFreeSpace(RelFileNode *rel,
 	fsm_record_free_space(fsmrel, oldPage, oldSpaceAvail);
 	/* Do the Get */
 	freepage = find_free_space(fsmrel, spaceNeeded);
-	SpinRelease(FreeSpaceLock);
+	LWLockRelease(FreeSpaceLock);
 	return freepage;
 }
 
@@ -378,7 +376,7 @@ MultiRecordFreeSpace(RelFileNode *rel,
 	FSMRelation *fsmrel;
 	int			i;
 
-	SpinAcquire(FreeSpaceLock);
+	LWLockAcquire(FreeSpaceLock, LW_EXCLUSIVE);
 	fsmrel = lookup_fsm_rel(rel);
 	if (fsmrel)
 	{
@@ -437,7 +435,7 @@ MultiRecordFreeSpace(RelFileNode *rel,
 				fsm_record_free_space(fsmrel, page, avail);
 		}
 	}
-	SpinRelease(FreeSpaceLock);
+	LWLockRelease(FreeSpaceLock);
 }
 
 /*
@@ -452,11 +450,11 @@ FreeSpaceMapForgetRel(RelFileNode *rel)
 {
 	FSMRelation *fsmrel;
 
-	SpinAcquire(FreeSpaceLock);
+	LWLockAcquire(FreeSpaceLock, LW_EXCLUSIVE);
 	fsmrel = lookup_fsm_rel(rel);
 	if (fsmrel)
 		delete_fsm_rel(fsmrel);
-	SpinRelease(FreeSpaceLock);
+	LWLockRelease(FreeSpaceLock);
 }
 
 /*
@@ -474,14 +472,14 @@ FreeSpaceMapForgetDatabase(Oid dbid)
 	FSMRelation *fsmrel,
 			   *nextrel;
 
-	SpinAcquire(FreeSpaceLock);
+	LWLockAcquire(FreeSpaceLock, LW_EXCLUSIVE);
 	for (fsmrel = FreeSpaceMap->relList; fsmrel; fsmrel = nextrel)
 	{
 		nextrel = fsmrel->nextRel; /* in case we delete it */
 		if (fsmrel->key.tblNode == dbid)
 			delete_fsm_rel(fsmrel);
 	}
-	SpinRelease(FreeSpaceLock);
+	LWLockRelease(FreeSpaceLock);
 }