From 2986aa6a668bce3cfb83606bb52e9d01ae66ad6c Mon Sep 17 00:00:00 2001
From: Bruce Momjian <bruce@momjian.us>
Date: Fri, 15 Nov 2002 02:44:57 +0000
Subject: [PATCH] Add checkpoint_warning to warn of excessive checkpoints
caused by too few WAL files.
---
doc/src/sgml/runtime.sgml | 14 ++++++++++++-
doc/src/sgml/wal.sgml | 12 ++++++++++-
src/backend/postmaster/postmaster.c | 20 ++++++++++++++++++-
src/backend/utils/misc/guc.c | 7 ++++++-
src/backend/utils/misc/postgresql.conf.sample | 1 +
src/include/access/xlog.h | 3 ++-
6 files changed, 52 insertions(+), 5 deletions(-)
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 6ca8f820e34..26777ae43a8 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -1,5 +1,5 @@
<!--
-$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.154 2002/11/15 01:57:25 momjian Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.155 2002/11/15 02:44:50 momjian Exp $
-->
<Chapter Id="runtime">
@@ -2081,6 +2081,18 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
</listitem>
</varlistentry>
+ <variablelist>
+ <varlistentry>
+ <term><varname>CHECKPOINT_WARNING</varname> (<type>integer</type>)</term>
+ <listitem>
+ <para>
+ Send a message to the server logs if checkpoints caused by the
+ filling of checkpoint segment files happens more frequently than
+ this number of seconds. Zero turns off the warning.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term><varname>COMMIT_DELAY</varname> (<type>integer</type>)</term>
<listitem>
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 7f603221acc..2589ab8163b 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -1,4 +1,4 @@
-<!-- $Header: /cvsroot/pgsql/doc/src/sgml/wal.sgml,v 1.21 2002/11/02 22:23:01 tgl Exp $ -->
+<!-- $Header: /cvsroot/pgsql/doc/src/sgml/wal.sgml,v 1.22 2002/11/15 02:44:54 momjian Exp $ -->
<chapter id="wal">
<title>Write-Ahead Logging (<acronym>WAL</acronym>)</title>
@@ -300,6 +300,16 @@
correspondingly increase shared memory usage.
</para>
+ <para>
+ Checkpoints are fairly expensive because they force all dirty kernel
+ buffers to disk using the operating system <literal>sync()</> call.
+ Busy servers may fill checkpoint segment files too quickly,
+ causing excessive checkpointing. If such forced checkpoints happen
+ more frequently than <varname>CHECKPOINT_WARNING</varname> seconds,
+ a message, will be output to the server logs recommending increasing
+ <varname>CHECKPOINT_SEGMENTS</varname>.
+ </para>
+
<para>
The <varname>COMMIT_DELAY</varname> parameter defines for how many
microseconds the backend will sleep after writing a commit
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index a9d18a575b8..53aa731e719 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -37,7 +37,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.296 2002/11/15 01:57:26 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.297 2002/11/15 02:44:55 momjian Exp $
*
* NOTES
*
@@ -198,6 +198,8 @@ bool SilentMode = false; /* silent mode (-S) */
int PreAuthDelay = 0;
int AuthenticationTimeout = 60;
int CheckPointTimeout = 300;
+int CheckPointWarning = 30;
+time_t LastSignalledCheckpoint = 0;
bool log_hostname; /* for ps display */
bool LogSourcePort;
@@ -2329,6 +2331,22 @@ sigusr1_handler(SIGNAL_ARGS)
if (CheckPostmasterSignal(PMSIGNAL_DO_CHECKPOINT))
{
+ if (CheckPointWarning != 0)
+ {
+ /*
+ * This only times checkpoints forced by running out of
+ * segment files. Other checkpoints could reduce
+ * the frequency of forced checkpoints.
+ */
+ time_t now = time(NULL);
+
+ if (now - LastSignalledCheckpoint < CheckPointWarning)
+ elog(LOG, "Checkpoint segments are being created too frequently (%d secs)\n
+ Consider increasing CHECKPOINT_SEGMENTS",
+ now - LastSignalledCheckpoint);
+ LastSignalledCheckpoint = now;
+ }
+
/*
* Request to schedule a checkpoint
*
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 96d42109e06..62417bfe118 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -5,7 +5,7 @@
* command, configuration file, and command line options.
* See src/backend/utils/misc/README for more information.
*
- * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.105 2002/11/15 01:57:27 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.106 2002/11/15 02:44:57 momjian Exp $
*
* Copyright 2000 by PostgreSQL Global Development Group
* Written by Peter Eisentraut <peter_e@gmx.net>.
@@ -660,6 +660,11 @@ static struct config_int
300, 30, 3600, NULL, NULL
},
+ {
+ {"checkpoint_warning", PGC_SIGHUP}, &CheckPointWarning,
+ 30, 0, INT_MAX, NULL, NULL
+ },
+
{
{"wal_buffers", PGC_POSTMASTER}, &XLOGbuffers,
8, 4, INT_MAX, NULL, NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index becc6dfbe74..5fbfafd214a 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -65,6 +65,7 @@
#
#checkpoint_segments = 3 # in logfile segments, min 1, 16MB each
#checkpoint_timeout = 300 # range 30-3600, in seconds
+#checkpoint_warning = 30 # 0 is off, in seconds
#
#commit_delay = 0 # range 0-100000, in microseconds
#commit_siblings = 5 # range 1-1000
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index f5c3e59cbce..1659c65b930 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: xlog.h,v 1.39 2002/09/26 22:58:34 tgl Exp $
+ * $Id: xlog.h,v 1.40 2002/11/15 02:44:57 momjian Exp $
*/
#ifndef XLOG_H
#define XLOG_H
@@ -184,6 +184,7 @@ extern XLogRecPtr ProcLastRecEnd;
/* these variables are GUC parameters related to XLOG */
extern int CheckPointSegments;
+extern int CheckPointWarning;
extern int XLOGbuffers;
extern int XLOG_DEBUG;
extern char *XLOG_sync_method;
--
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