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Commit61b8614

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Modify MoveOfflineLogs/InstallXLogFileSegment to avoid O(N^2) behavior
when recycling a large number of xlog segments during checkpoint.The former behavior searched from the same start point each time,requiring O(checkpoint_segments^2) stat() calls to relocate all thesegments. Instead keep track of where we stopped last time through.
1 parent348f856 commit61b8614

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1 file changed

+37
-23
lines changed
  • src/backend/access/transam

1 file changed

+37
-23
lines changed

‎src/backend/access/transam/xlog.c

Lines changed: 37 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.184 2005/04/13 18:54:56 tgl Exp $
10+
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.185 2005/04/15 18:48:10 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -444,8 +444,8 @@ static bool AdvanceXLInsertBuffer(void);
444444
staticvoidXLogWrite(XLogwrtRqstWriteRqst);
445445
staticintXLogFileInit(uint32log,uint32seg,
446446
bool*use_existent,booluse_lock);
447-
staticboolInstallXLogFileSegment(uint32log,uint32seg,char*tmppath,
448-
boolfind_free,intmax_advance,
447+
staticboolInstallXLogFileSegment(uint32*log,uint32*seg,char*tmppath,
448+
boolfind_free,int*max_advance,
449449
booluse_lock);
450450
staticintXLogFileOpen(uint32log,uint32seg);
451451
staticintXLogFileRead(uint32log,uint32seg,intemode);
@@ -1509,6 +1509,9 @@ XLogFileInit(uint32 log, uint32 seg,
15091509
charpath[MAXPGPATH];
15101510
chartmppath[MAXPGPATH];
15111511
charzbuffer[BLCKSZ];
1512+
uint32installed_log;
1513+
uint32installed_seg;
1514+
intmax_advance;
15121515
intfd;
15131516
intnbytes;
15141517

@@ -1601,8 +1604,11 @@ XLogFileInit(uint32 log, uint32 seg,
16011604
* else has created the file while we were filling ours: if so, use
16021605
* ours to pre-create a future log segment.
16031606
*/
1604-
if (!InstallXLogFileSegment(log,seg,tmppath,
1605-
*use_existent,XLOGfileslop,
1607+
installed_log=log;
1608+
installed_seg=seg;
1609+
max_advance=XLOGfileslop;
1610+
if (!InstallXLogFileSegment(&installed_log,&installed_seg,tmppath,
1611+
*use_existent,&max_advance,
16061612
use_lock))
16071613
{
16081614
/* No need for any more future segments... */
@@ -1722,7 +1728,7 @@ XLogFileCopy(uint32 log, uint32 seg,
17221728
/*
17231729
* Now move the segment into place with its final name.
17241730
*/
1725-
if (!InstallXLogFileSegment(log,seg,tmppath, false,0, false))
1731+
if (!InstallXLogFileSegment(&log,&seg,tmppath, false,NULL, false))
17261732
elog(PANIC,"InstallXLogFileSegment should not have failed");
17271733
}
17281734

@@ -1732,17 +1738,20 @@ XLogFileCopy(uint32 log, uint32 seg,
17321738
* This is used both to install a newly-created segment (which has a temp
17331739
* filename while it's being created) and to recycle an old segment.
17341740
*
1735-
* log, seg: identify segment to install as (or first possible target).
1741+
* *log, *seg: identify segment to install as (or first possible target).
1742+
* When find_free is TRUE, these are modified on return to indicate the
1743+
* actual installation location or last segment searched.
17361744
*
17371745
* tmppath: initial name of file to install. It will be renamed into place.
17381746
*
17391747
* find_free: if TRUE, install the new segment at the first empty log/seg
17401748
* number at or after the passed numbers. If FALSE, install the new segment
17411749
* exactly where specified, deleting any existing segment file there.
17421750
*
1743-
* max_advance: maximum number of log/seg slots to advance past the starting
1744-
* point. Fail if no free slot is found in this range. (Irrelevant if
1745-
* find_free is FALSE.)
1751+
* *max_advance: maximum number of log/seg slots to advance past the starting
1752+
* point. Fail if no free slot is found in this range. On return, reduced
1753+
* by the number of slots skipped over. (Irrelevant, and may be NULL,
1754+
* when find_free is FALSE.)
17461755
*
17471756
* use_lock: if TRUE, acquire ControlFileLock while moving file into
17481757
* place. This should be TRUE except during bootstrap log creation. The
@@ -1752,14 +1761,14 @@ XLogFileCopy(uint32 log, uint32 seg,
17521761
* exceeding max_advance limit. (Any other kind of failure causes ereport().)
17531762
*/
17541763
staticbool
1755-
InstallXLogFileSegment(uint32log,uint32seg,char*tmppath,
1756-
boolfind_free,intmax_advance,
1764+
InstallXLogFileSegment(uint32*log,uint32*seg,char*tmppath,
1765+
boolfind_free,int*max_advance,
17571766
booluse_lock)
17581767
{
17591768
charpath[MAXPGPATH];
17601769
structstatstat_buf;
17611770

1762-
XLogFilePath(path,ThisTimeLineID,log,seg);
1771+
XLogFilePath(path,ThisTimeLineID,*log,*seg);
17631772

17641773
/*
17651774
* We want to be sure that only one process does this at a time.
@@ -1777,15 +1786,16 @@ InstallXLogFileSegment(uint32 log, uint32 seg, char *tmppath,
17771786
/* Find a free slot to put it in */
17781787
while (stat(path,&stat_buf)==0)
17791788
{
1780-
if (--max_advance<0)
1789+
if (*max_advance <=0)
17811790
{
17821791
/* Failed to find a free slot within specified range */
17831792
if (use_lock)
17841793
LWLockRelease(ControlFileLock);
17851794
return false;
17861795
}
1787-
NextLogSeg(log,seg);
1788-
XLogFilePath(path,ThisTimeLineID,log,seg);
1796+
NextLogSeg(*log,*seg);
1797+
(*max_advance)--;
1798+
XLogFilePath(path,ThisTimeLineID,*log,*seg);
17891799
}
17901800
}
17911801

@@ -1799,14 +1809,14 @@ InstallXLogFileSegment(uint32 log, uint32 seg, char *tmppath,
17991809
ereport(PANIC,
18001810
(errcode_for_file_access(),
18011811
errmsg("could not link file \"%s\" to \"%s\" (initialization of log file %u, segment %u): %m",
1802-
tmppath,path,log,seg)));
1812+
tmppath,path,*log,*seg)));
18031813
unlink(tmppath);
18041814
#else
18051815
if (rename(tmppath,path)<0)
18061816
ereport(PANIC,
18071817
(errcode_for_file_access(),
18081818
errmsg("could not rename file \"%s\" to \"%s\" (initialization of log file %u, segment %u): %m",
1809-
tmppath,path,log,seg)));
1819+
tmppath,path,*log,*seg)));
18101820
#endif
18111821

18121822
if (use_lock)
@@ -2129,6 +2139,7 @@ MoveOfflineLogs(uint32 log, uint32 seg, XLogRecPtr endptr,
21292139
{
21302140
uint32endlogId;
21312141
uint32endlogSeg;
2142+
intmax_advance;
21322143
DIR*xldir;
21332144
structdirent*xlde;
21342145
charlastoff[MAXFNAMELEN];
@@ -2137,7 +2148,12 @@ MoveOfflineLogs(uint32 log, uint32 seg, XLogRecPtr endptr,
21372148
*nsegsremoved=0;
21382149
*nsegsrecycled=0;
21392150

2151+
/*
2152+
* Initialize info about where to try to recycle to. We allow recycling
2153+
* segments up to XLOGfileslop segments beyond the current XLOG location.
2154+
*/
21402155
XLByteToPrevSeg(endptr,endlogId,endlogSeg);
2156+
max_advance=XLOGfileslop;
21412157

21422158
xldir=AllocateDir(XLogDir);
21432159
if (xldir==NULL)
@@ -2179,12 +2195,10 @@ MoveOfflineLogs(uint32 log, uint32 seg, XLogRecPtr endptr,
21792195

21802196
/*
21812197
* Before deleting the file, see if it can be recycled as
2182-
* a future log segment. We allow recycling segments up
2183-
* to XLOGfileslop segments beyond the current XLOG
2184-
* location.
2198+
* a future log segment.
21852199
*/
2186-
if (InstallXLogFileSegment(endlogId,endlogSeg,path,
2187-
true,XLOGfileslop,
2200+
if (InstallXLogFileSegment(&endlogId,&endlogSeg,path,
2201+
true,&max_advance,
21882202
true))
21892203
{
21902204
ereport(DEBUG2,

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