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Arrange to call AbsorbFsyncRequests every so often while performing a

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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.
This commit is contained in:
Tom Lane
2006-03-03 00:02:02 +00:00
parent f0bfc02001
commit 9a506a6257
2 changed files with 40 additions and 3 deletions
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23
src/backend/storage/buffer/bufmgr.c
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@@ -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;
}