Replace the BufMgrLock with separate locks on the lookup hashtable and

the freelist, plus per-buffer spinlocks that protect access to individual
shared buffer headers.  This requires abandoning a global freelist (since
the freelist is a global contention point), which shoots down ARC and 2Q
as well as plain LRU management.  Adopt a clock sweep algorithm instead.
Preliminary results show substantial improvement in multi-backend situations.

1 files changed, 2 insertions, 7 deletions

diff --git a/src/backend/utils/resowner/resowner.c b/src/backend/utils/resowner/resowner.c
index 5f1f99f703..f3063ed9d9 100644
--- a/src/backend/utils/resowner/resowner.c
+++ b/src/backend/utils/resowner/resowner.c
@@ -14,7 +14,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/resowner/resowner.c,v 1.9 2004/12/31 22:02:50 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/resowner/resowner.c,v 1.10 2005/03/04 20:21:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -200,12 +200,7 @@ ResourceOwnerReleaseInternal(ResourceOwner owner,
 		 * that would indicate failure to clean up the executor correctly ---
 		 * so issue warnings.  In the abort case, just clean up quietly.
 		 *
-		 * XXX this is fairly inefficient due to multiple BufMgrLock
-		 * grabs if there are lots of buffers to be released, but we
-		 * don't expect many (indeed none in the success case) so it's
-		 * probably not worth optimizing.
-		 *
-		 * We are however careful to release back-to-front, so as to
+		 * We are careful to do the releasing back-to-front, so as to
 		 * avoid O(N^2) behavior in ResourceOwnerForgetBuffer().
 		 */
 		while (owner->nbuffers > 0)