Just-in-time background writing strategy. This code avoids re-scanning

buffers that cannot possibly need to be cleaned, and estimates how many
buffers it should try to clean based on moving averages of recent allocation
requests and density of reusable buffers.  The patch also adds a couple
more columns to pg_stat_bgwriter to help measure the effectiveness of the
bgwriter.

Greg Smith, building on his own work and ideas from several other people,
in particular a much older patch from Itagaki Takahiro.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 2f53fdcd7c..2d3c698953 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -5,7 +5,7 @@
  *
  *	Copyright (c) 2001-2007, PostgreSQL Global Development Group
  *
- *	$PostgreSQL: pgsql/src/include/pgstat.h,v 1.67 2007/09/24 03:12:23 tgl Exp $
+ *	$PostgreSQL: pgsql/src/include/pgstat.h,v 1.68 2007/09/25 20:03:38 tgl Exp $
  * ----------
  */
 #ifndef PGSTAT_H
@@ -294,6 +294,8 @@ typedef struct PgStat_MsgBgWriter
 	PgStat_Counter	m_buf_written_checkpoints;
 	PgStat_Counter	m_buf_written_clean;
 	PgStat_Counter	m_maxwritten_clean;
+	PgStat_Counter  m_buf_written_backend;
+	PgStat_Counter  m_buf_alloc;
 } PgStat_MsgBgWriter;
 
 
@@ -394,6 +396,8 @@ typedef struct PgStat_GlobalStats
 	PgStat_Counter  buf_written_checkpoints;
 	PgStat_Counter  buf_written_clean;
 	PgStat_Counter  maxwritten_clean;
+	PgStat_Counter  buf_written_backend;
+	PgStat_Counter  buf_alloc;
 } PgStat_GlobalStats;