From 9a506a6257f3874d07cd185bec981f2ad335fc54 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 3 Mar 2006 00:02:02 +0000
Subject: [PATCH] Arrange to call AbsorbFsyncRequests every so often while
performing a checkpoint in the bgwriter. This forestalls overflow of the
fsync request queue, which is not fatal but causes considerable performance
degradation when it occurs (because backends then have to do their own
fsyncs). Per patch from Itagaki Takahiro, modified a little bit by me.
---
src/backend/storage/buffer/bufmgr.c | 23 +++++++++++++++++++++--
src/backend/storage/smgr/md.c | 20 +++++++++++++++++++-
2 files changed, 40 insertions(+), 3 deletions(-)
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 11e83812d0c..41ca4c14495 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 1.202 2006/01/06 00:04:20 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.203 2006/03/03 00:02:01 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -42,6 +42,7 @@
#include "lib/stringinfo.h"
#include "miscadmin.h"
+#include "postmaster/bgwriter.h"
#include "storage/buf_internals.h"
#include "storage/bufmgr.h"
#include "storage/bufpage.h"
@@ -61,6 +62,9 @@
#define LocalBufHdrGetBlock(bufHdr) \
LocalBufferBlockPointers[-((bufHdr)->buf_id + 2)]
+/* interval for calling AbsorbFsyncRequests in BufferSync */
+#define WRITES_PER_ABSORB 1000
+
/* GUC variables */
bool zero_damaged_pages = false;
@@ -892,6 +896,7 @@ BufferSync(void)
{
int buf_id;
int num_to_scan;
+ int absorb_counter;
/*
* Find out where to start the circular scan.
@@ -905,9 +910,23 @@ BufferSync(void)
* Loop over all buffers.
*/
num_to_scan = NBuffers;
+ absorb_counter = WRITES_PER_ABSORB;
while (num_to_scan-- > 0)
{
- (void) SyncOneBuffer(buf_id, false);
+ if (SyncOneBuffer(buf_id, false))
+ {
+ /*
+ * If in bgwriter, absorb pending fsync requests after each
+ * WRITES_PER_ABSORB write operations, to prevent overflow of
+ * the fsync request queue. If not in bgwriter process, this is
+ * a no-op.
+ */
+ if (--absorb_counter <= 0)
+ {
+ AbsorbFsyncRequests();
+ absorb_counter = WRITES_PER_ABSORB;
+ }
+ }
if (++buf_id >= NBuffers)
buf_id = 0;
}
diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index f8d15ee3ff8..60d8a229639 100644
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/smgr/md.c,v 1.118 2005/10/15 02:49:26 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/smgr/md.c,v 1.119 2006/03/03 00:02:02 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -28,6 +28,9 @@
#include "utils/memutils.h"
+/* interval for calling AbsorbFsyncRequests in mdsync */
+#define FSYNCS_PER_ABSORB 10
+
/*
* The magnetic disk storage manager keeps track of open file
* descriptors in its own descriptor pool. This is done to make it
@@ -702,6 +705,7 @@ mdsync(void)
{
HASH_SEQ_STATUS hstat;
PendingOperationEntry *entry;
+ int absorb_counter;
if (!pendingOpsTable)
return false;
@@ -714,6 +718,7 @@ mdsync(void)
*/
AbsorbFsyncRequests();
+ absorb_counter = FSYNCS_PER_ABSORB;
hash_seq_init(&hstat, pendingOpsTable);
while ((entry = (PendingOperationEntry *) hash_seq_search(&hstat)) != NULL)
{
@@ -727,6 +732,19 @@ mdsync(void)
SMgrRelation reln;
MdfdVec *seg;
+ /*
+ * If in bgwriter, absorb pending requests every so often to
+ * prevent overflow of the fsync request queue. The hashtable
+ * code does not specify whether entries added by this will be
+ * visited by our search, but we don't really care: it's OK if
+ * we do, and OK if we don't.
+ */
+ if (--absorb_counter <= 0)
+ {
+ AbsorbFsyncRequests();
+ absorb_counter = FSYNCS_PER_ABSORB;
+ }
+
/*
* Find or create an smgr hash entry for this relation. This may
* seem a bit unclean -- md calling smgr? But it's really the
--
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