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 the segments. Instead keep track of where we stopped last time through.
This commit is contained in:
Tom Lane
parent
348f856dc5
commit
61b861421b
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.184 2005/04/13 18:54:56 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.185 2005/04/15 18:48:10 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -444,8 +444,8 @@ static bool AdvanceXLInsertBuffer(void);
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static void XLogWrite(XLogwrtRqst WriteRqst);
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static int XLogFileInit(uint32 log, uint32 seg,
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bool *use_existent, bool use_lock);
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static bool InstallXLogFileSegment(uint32 log, uint32 seg, char *tmppath,
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bool find_free, int max_advance,
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static bool InstallXLogFileSegment(uint32 *log, uint32 *seg, char *tmppath,
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bool find_free, int *max_advance,
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bool use_lock);
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static int XLogFileOpen(uint32 log, uint32 seg);
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static int XLogFileRead(uint32 log, uint32 seg, int emode);
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@ -1509,6 +1509,9 @@ XLogFileInit(uint32 log, uint32 seg,
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char path[MAXPGPATH];
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char tmppath[MAXPGPATH];
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char zbuffer[BLCKSZ];
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uint32 installed_log;
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uint32 installed_seg;
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int max_advance;
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int fd;
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int nbytes;
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@ -1601,8 +1604,11 @@ XLogFileInit(uint32 log, uint32 seg,
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* else has created the file while we were filling ours: if so, use
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* ours to pre-create a future log segment.
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*/
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if (!InstallXLogFileSegment(log, seg, tmppath,
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*use_existent, XLOGfileslop,
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installed_log = log;
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installed_seg = seg;
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max_advance = XLOGfileslop;
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if (!InstallXLogFileSegment(&installed_log, &installed_seg, tmppath,
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*use_existent, &max_advance,
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use_lock))
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{
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/* No need for any more future segments... */
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@ -1722,7 +1728,7 @@ XLogFileCopy(uint32 log, uint32 seg,
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/*
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* Now move the segment into place with its final name.
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*/
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if (!InstallXLogFileSegment(log, seg, tmppath, false, 0, false))
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if (!InstallXLogFileSegment(&log, &seg, tmppath, false, NULL, false))
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elog(PANIC, "InstallXLogFileSegment should not have failed");
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}
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@ -1732,7 +1738,9 @@ XLogFileCopy(uint32 log, uint32 seg,
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* This is used both to install a newly-created segment (which has a temp
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* filename while it's being created) and to recycle an old segment.
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*
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* log, seg: identify segment to install as (or first possible target).
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* *log, *seg: identify segment to install as (or first possible target).
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* When find_free is TRUE, these are modified on return to indicate the
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* actual installation location or last segment searched.
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*
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* tmppath: initial name of file to install. It will be renamed into place.
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*
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@ -1740,9 +1748,10 @@ XLogFileCopy(uint32 log, uint32 seg,
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* number at or after the passed numbers. If FALSE, install the new segment
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* exactly where specified, deleting any existing segment file there.
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*
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* max_advance: maximum number of log/seg slots to advance past the starting
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* point. Fail if no free slot is found in this range. (Irrelevant if
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* find_free is FALSE.)
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* *max_advance: maximum number of log/seg slots to advance past the starting
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* point. Fail if no free slot is found in this range. On return, reduced
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* by the number of slots skipped over. (Irrelevant, and may be NULL,
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* when find_free is FALSE.)
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*
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* use_lock: if TRUE, acquire ControlFileLock while moving file into
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* place. This should be TRUE except during bootstrap log creation. The
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@ -1752,14 +1761,14 @@ XLogFileCopy(uint32 log, uint32 seg,
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* exceeding max_advance limit. (Any other kind of failure causes ereport().)
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*/
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static bool
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InstallXLogFileSegment(uint32 log, uint32 seg, char *tmppath,
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bool find_free, int max_advance,
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InstallXLogFileSegment(uint32 *log, uint32 *seg, char *tmppath,
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bool find_free, int *max_advance,
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bool use_lock)
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{
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char path[MAXPGPATH];
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struct stat stat_buf;
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XLogFilePath(path, ThisTimeLineID, log, seg);
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XLogFilePath(path, ThisTimeLineID, *log, *seg);
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/*
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* We want to be sure that only one process does this at a time.
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@ -1777,15 +1786,16 @@ InstallXLogFileSegment(uint32 log, uint32 seg, char *tmppath,
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/* Find a free slot to put it in */
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while (stat(path, &stat_buf) == 0)
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{
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if (--max_advance < 0)
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if (*max_advance <= 0)
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{
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/* Failed to find a free slot within specified range */
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if (use_lock)
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LWLockRelease(ControlFileLock);
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return false;
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}
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NextLogSeg(log, seg);
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XLogFilePath(path, ThisTimeLineID, log, seg);
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NextLogSeg(*log, *seg);
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(*max_advance)--;
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XLogFilePath(path, ThisTimeLineID, *log, *seg);
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}
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}
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@ -1799,14 +1809,14 @@ InstallXLogFileSegment(uint32 log, uint32 seg, char *tmppath,
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ereport(PANIC,
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(errcode_for_file_access(),
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errmsg("could not link file \"%s\" to \"%s\" (initialization of log file %u, segment %u): %m",
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tmppath, path, log, seg)));
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tmppath, path, *log, *seg)));
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unlink(tmppath);
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#else
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if (rename(tmppath, path) < 0)
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ereport(PANIC,
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(errcode_for_file_access(),
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errmsg("could not rename file \"%s\" to \"%s\" (initialization of log file %u, segment %u): %m",
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tmppath, path, log, seg)));
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tmppath, path, *log, *seg)));
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#endif
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if (use_lock)
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@ -2129,6 +2139,7 @@ MoveOfflineLogs(uint32 log, uint32 seg, XLogRecPtr endptr,
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{
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uint32 endlogId;
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uint32 endlogSeg;
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int max_advance;
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DIR *xldir;
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struct dirent *xlde;
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char lastoff[MAXFNAMELEN];
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@ -2137,7 +2148,12 @@ MoveOfflineLogs(uint32 log, uint32 seg, XLogRecPtr endptr,
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*nsegsremoved = 0;
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*nsegsrecycled = 0;
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/*
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* Initialize info about where to try to recycle to. We allow recycling
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* segments up to XLOGfileslop segments beyond the current XLOG location.
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*/
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XLByteToPrevSeg(endptr, endlogId, endlogSeg);
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max_advance = XLOGfileslop;
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xldir = AllocateDir(XLogDir);
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if (xldir == NULL)
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@ -2179,12 +2195,10 @@ MoveOfflineLogs(uint32 log, uint32 seg, XLogRecPtr endptr,
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/*
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* Before deleting the file, see if it can be recycled as
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* a future log segment. We allow recycling segments up
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* to XLOGfileslop segments beyond the current XLOG
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* location.
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* a future log segment.
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*/
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if (InstallXLogFileSegment(endlogId, endlogSeg, path,
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true, XLOGfileslop,
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if (InstallXLogFileSegment(&endlogId, &endlogSeg, path,
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true, &max_advance,
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true))
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{
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ereport(DEBUG2,
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