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Modify MoveOfflineLogs/InstallXLogFileSegment to avoid O(N^2) behavior

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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 2005-04-15 18:48:10 +00:00
parent 348f856dc5
commit 61b861421b
1 changed files with 37 additions and 23 deletions
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60
src/backend/access/transam/xlog.c
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California * Portions Copyright (c) 1994, Regents of the University of California
* *
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.184 2005/04/13 18:54:56 tgl Exp $ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.185 2005/04/15 18:48:10 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -444,8 +444,8 @@ static bool AdvanceXLInsertBuffer(void);
static void XLogWrite(XLogwrtRqst WriteRqst); static void XLogWrite(XLogwrtRqst WriteRqst);
static int XLogFileInit(uint32 log, uint32 seg, static int XLogFileInit(uint32 log, uint32 seg,
bool *use_existent, bool use_lock); bool *use_existent, bool use_lock);
static bool InstallXLogFileSegment(uint32 log, uint32 seg, char *tmppath, static bool InstallXLogFileSegment(uint32 *log, uint32 *seg, char *tmppath,
bool find_free, int max_advance, bool find_free, int *max_advance,
bool use_lock); bool use_lock);
static int XLogFileOpen(uint32 log, uint32 seg); static int XLogFileOpen(uint32 log, uint32 seg);
static int XLogFileRead(uint32 log, uint32 seg, int emode); static int XLogFileRead(uint32 log, uint32 seg, int emode);
@ -1509,6 +1509,9 @@ XLogFileInit(uint32 log, uint32 seg,
char path[MAXPGPATH]; char path[MAXPGPATH];
char tmppath[MAXPGPATH]; char tmppath[MAXPGPATH];
char zbuffer[BLCKSZ]; char zbuffer[BLCKSZ];
uint32 installed_log;
uint32 installed_seg;
int max_advance;
int fd; int fd;
int nbytes; int nbytes;
@ -1601,8 +1604,11 @@ XLogFileInit(uint32 log, uint32 seg,
* else has created the file while we were filling ours: if so, use * else has created the file while we were filling ours: if so, use
* ours to pre-create a future log segment. * ours to pre-create a future log segment.
*/ */
if (!InstallXLogFileSegment(log, seg, tmppath, installed_log = log;
*use_existent, XLOGfileslop, installed_seg = seg;
max_advance = XLOGfileslop;
if (!InstallXLogFileSegment(&installed_log, &installed_seg, tmppath,
*use_existent, &max_advance,
use_lock)) use_lock))
{ {
/* No need for any more future segments... */ /* No need for any more future segments... */
@ -1722,7 +1728,7 @@ XLogFileCopy(uint32 log, uint32 seg,
/* /*
* Now move the segment into place with its final name. * Now move the segment into place with its final name.
*/ */
if (!InstallXLogFileSegment(log, seg, tmppath, false, 0, false)) if (!InstallXLogFileSegment(&log, &seg, tmppath, false, NULL, false))
elog(PANIC, "InstallXLogFileSegment should not have failed"); elog(PANIC, "InstallXLogFileSegment should not have failed");
} }
@ -1732,7 +1738,9 @@ XLogFileCopy(uint32 log, uint32 seg,
* This is used both to install a newly-created segment (which has a temp * This is used both to install a newly-created segment (which has a temp
* filename while it's being created) and to recycle an old segment. * filename while it's being created) and to recycle an old segment.
* *
* log, seg: identify segment to install as (or first possible target). * *log, *seg: identify segment to install as (or first possible target).
* When find_free is TRUE, these are modified on return to indicate the
* actual installation location or last segment searched.
* *
* tmppath: initial name of file to install. It will be renamed into place. * tmppath: initial name of file to install. It will be renamed into place.
* *
@ -1740,9 +1748,10 @@ XLogFileCopy(uint32 log, uint32 seg,
* number at or after the passed numbers. If FALSE, install the new segment * number at or after the passed numbers. If FALSE, install the new segment
* exactly where specified, deleting any existing segment file there. * exactly where specified, deleting any existing segment file there.
* *
* max_advance: maximum number of log/seg slots to advance past the starting * *max_advance: maximum number of log/seg slots to advance past the starting
* point. Fail if no free slot is found in this range. (Irrelevant if * point. Fail if no free slot is found in this range. On return, reduced
* find_free is FALSE.) * by the number of slots skipped over. (Irrelevant, and may be NULL,
* when find_free is FALSE.)
* *
* use_lock: if TRUE, acquire ControlFileLock while moving file into * use_lock: if TRUE, acquire ControlFileLock while moving file into
* place. This should be TRUE except during bootstrap log creation. The * place. This should be TRUE except during bootstrap log creation. The
@ -1752,14 +1761,14 @@ XLogFileCopy(uint32 log, uint32 seg,
* exceeding max_advance limit. (Any other kind of failure causes ereport().) * exceeding max_advance limit. (Any other kind of failure causes ereport().)
*/ */
static bool static bool
InstallXLogFileSegment(uint32 log, uint32 seg, char *tmppath, InstallXLogFileSegment(uint32 *log, uint32 *seg, char *tmppath,
bool find_free, int max_advance, bool find_free, int *max_advance,
bool use_lock) bool use_lock)
{ {
char path[MAXPGPATH]; char path[MAXPGPATH];
struct stat stat_buf; struct stat stat_buf;
XLogFilePath(path, ThisTimeLineID, log, seg); XLogFilePath(path, ThisTimeLineID, *log, *seg);
/* /*
* We want to be sure that only one process does this at a time. * 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,
/* Find a free slot to put it in */ /* Find a free slot to put it in */
while (stat(path, &stat_buf) == 0) while (stat(path, &stat_buf) == 0)
{ {
if (--max_advance < 0) if (*max_advance <= 0)
{ {
/* Failed to find a free slot within specified range */ /* Failed to find a free slot within specified range */
if (use_lock) if (use_lock)
LWLockRelease(ControlFileLock); LWLockRelease(ControlFileLock);
return false; return false;
} }
NextLogSeg(log, seg); NextLogSeg(*log, *seg);
XLogFilePath(path, ThisTimeLineID, log, seg); (*max_advance)--;
XLogFilePath(path, ThisTimeLineID, *log, *seg);
} }
} }
@ -1799,14 +1809,14 @@ InstallXLogFileSegment(uint32 log, uint32 seg, char *tmppath,
ereport(PANIC, ereport(PANIC,
(errcode_for_file_access(), (errcode_for_file_access(),
errmsg("could not link file \"%s\" to \"%s\" (initialization of log file %u, segment %u): %m", errmsg("could not link file \"%s\" to \"%s\" (initialization of log file %u, segment %u): %m",
tmppath, path, log, seg))); tmppath, path, *log, *seg)));
unlink(tmppath); unlink(tmppath);
#else #else
if (rename(tmppath, path) < 0) if (rename(tmppath, path) < 0)
ereport(PANIC, ereport(PANIC,
(errcode_for_file_access(), (errcode_for_file_access(),
errmsg("could not rename file \"%s\" to \"%s\" (initialization of log file %u, segment %u): %m", errmsg("could not rename file \"%s\" to \"%s\" (initialization of log file %u, segment %u): %m",
tmppath, path, log, seg))); tmppath, path, *log, *seg)));
#endif #endif
if (use_lock) if (use_lock)
@ -2129,6 +2139,7 @@ MoveOfflineLogs(uint32 log, uint32 seg, XLogRecPtr endptr,
{ {
uint32 endlogId; uint32 endlogId;
uint32 endlogSeg; uint32 endlogSeg;
int max_advance;
DIR *xldir; DIR *xldir;
struct dirent *xlde; struct dirent *xlde;
char lastoff[MAXFNAMELEN]; char lastoff[MAXFNAMELEN];
@ -2137,7 +2148,12 @@ MoveOfflineLogs(uint32 log, uint32 seg, XLogRecPtr endptr,
*nsegsremoved = 0; *nsegsremoved = 0;
*nsegsrecycled = 0; *nsegsrecycled = 0;
/*
* Initialize info about where to try to recycle to. We allow recycling
* segments up to XLOGfileslop segments beyond the current XLOG location.
*/
XLByteToPrevSeg(endptr, endlogId, endlogSeg); XLByteToPrevSeg(endptr, endlogId, endlogSeg);
max_advance = XLOGfileslop;
xldir = AllocateDir(XLogDir); xldir = AllocateDir(XLogDir);
if (xldir == NULL) if (xldir == NULL)
@ -2179,12 +2195,10 @@ MoveOfflineLogs(uint32 log, uint32 seg, XLogRecPtr endptr,
/* /*
* Before deleting the file, see if it can be recycled as * Before deleting the file, see if it can be recycled as
* a future log segment. We allow recycling segments up * a future log segment.
* to XLOGfileslop segments beyond the current XLOG
* location.
*/ */
if (InstallXLogFileSegment(endlogId, endlogSeg, path, if (InstallXLogFileSegment(&endlogId, &endlogSeg, path,
true, XLOGfileslop, true, &max_advance,
true)) true))
{ {
ereport(DEBUG2, ereport(DEBUG2,