Allow background writing to be shut down by setting limit values to zero.

This does not disable the bgwriter process: it still has to wake up often
enough to collect fsync requests from backends in a timely fashion.  But
it responds to the recent gripe about not being able to prevent the disk
from being spun up constantly.

1 files changed, 9 insertions, 3 deletions

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index b9d8fc3ad53..c96c635d0a6 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.180 2004/10/16 18:57:23 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.181 2004/10/17 22:01:50 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -671,8 +671,10 @@ UnpinBuffer(BufferDesc *buf, bool fixOwner)
  *
  * This is called at checkpoint time to write out all dirty shared buffers,
  * and by the background writer process to write out some of the dirty blocks.
- * percent/maxpages should be zero in the former case, and nonzero limit
- * values in the latter.
+ * percent/maxpages should be -1 in the former case, and limit values (>= 0)
+ * in the latter.
+ *
+ * Returns the number of buffers written.
  */
 int
 BufferSync(int percent, int maxpages)
@@ -682,6 +684,10 @@ BufferSync(int percent, int maxpages)
 	int			num_buffer_dirty;
 	int			i;
 
+	/* If either limit is zero then we are disabled from doing anything... */
+	if (percent == 0 || maxpages == 0)
+		return 0;
+
 	/*
 	 * Get a list of all currently dirty buffers and how many there are.
 	 * We do not flush buffers that get dirtied after we started. They