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Implement COMMIT_SIBLINGS parameter to allow pre-commit delay to occur

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only if at least N other backends currently have open transactions.  This
is not a great deal of intelligence about whether a delay might be
profitable ... but it beats no intelligence at all.  Note that the default
COMMIT_DELAY is still zero --- this new code does nothing unless that
setting is changed.
Also, mark ENABLEFSYNC as a system-wide setting.  It's no longer safe to
allow that to be set per-backend, since we may be relying on some other
backend's fsync to have synced the WAL log.
This commit is contained in:
Tom Lane
2001-02-26 00:50:08 +00:00
parent 60774e8210
commit 9c9936587c
10 changed files with 94 additions and 31 deletions
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22
src/backend/access/transam/xact.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.97 2001/02/18 04:50:43 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.98 2001/02/26 00:50:07 tgl Exp $
*
* NOTES
* Transaction aborts can now occur two ways:
@ -157,6 +157,7 @@
#include <sys/time.h>
#include "access/nbtree.h"
#include "access/xact.h"
#include "catalog/heap.h"
#include "catalog/index.h"
#include "commands/async.h"
@ -177,8 +178,6 @@
extern bool SharedBufferChanged;
void RecordTransactionCommit(void);
static void AbortTransaction(void);
static void AtAbort_Cache(void);
static void AtAbort_Locks(void);
@ -216,12 +215,14 @@ TransactionStateData CurrentTransactionStateData = {
TransactionState CurrentTransactionState = &CurrentTransactionStateData;
/*
* User-tweakable parameters
*/
int DefaultXactIsoLevel = XACT_READ_COMMITTED;
int XactIsoLevel;
#include "access/xlogutils.h"
int CommitDelay = 0; /* in microseconds */
int CommitDelay = 0; /* precommit delay in microseconds */
int CommitSiblings = 5; /* number of concurrent xacts needed to sleep */
static void (*_RollbackFunc)(void*) = NULL;
static void *_RollbackData = NULL;
@ -687,10 +688,15 @@ RecordTransactionCommit()
* Sleep before commit! So we can flush more than one
* commit records per single fsync. (The idea is some other
* backend may do the XLogFlush while we're sleeping. This
* needs work however, because on most Unixen, the minimum
* needs work still, because on most Unixen, the minimum
* select() delay is 10msec or more, which is way too long.)
*
* We do not sleep if enableFsync is not turned on, nor if there
* are fewer than CommitSiblings other backends with active
* transactions.
*/
if (CommitDelay > 0)
if (CommitDelay > 0 && enableFsync &&
CountActiveBackends() >= CommitSiblings)
{
struct timeval delay;

4
src/backend/access/transam/xlog.c
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@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.54 2001/02/18 04:39:42 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.55 2001/02/26 00:50:07 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -2096,8 +2096,6 @@ ShutdownXLOG()
elog(LOG, "database system is shut down");
}
extern XLogRecPtr GetUndoRecPtr(void);
void
CreateCheckPoint(bool shutdown)
{

53
src/backend/storage/ipc/sinval.c
View File

@ -8,16 +8,14 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.25 2001/01/24 19:43:07 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.26 2001/02/26 00:50:07 tgl Exp $
*
*-------------------------------------------------------------------------
*/
/* #define INVALIDDEBUG 1 */
#include "postgres.h"
#include <sys/types.h>
#include "postgres.h"
#include "storage/backendid.h"
#include "storage/proc.h"
#include "storage/sinval.h"
@ -347,11 +345,54 @@ GetSnapshotData(bool serializable)
return snapshot;
}
/*
* CountActiveBackends --- count backends (other than myself) that are in
* active transactions. This is used as a heuristic to decide if
* a pre-XLOG-flush delay is worthwhile during commit.
*
* An active transaction is something that has written at least one XLOG
* record; read-only transactions don't count. Also, do not count backends
* that are blocked waiting for locks, since they are not going to get to
* run until someone else commits.
*/
int
CountActiveBackends(void)
{
SISeg *segP = shmInvalBuffer;
ProcState *stateP = segP->procState;
int count = 0;
int index;
/*
* Note: for speed, we don't acquire SInvalLock. This is a little bit
* bogus, but since we are only testing xrecoff for zero or nonzero,
* it should be OK. The result is only used for heuristic purposes
* anyway...
*/
for (index = 0; index < segP->lastBackend; index++)
{
SHMEM_OFFSET pOffset = stateP[index].procStruct;
if (pOffset != INVALID_OFFSET)
{
PROC *proc = (PROC *) MAKE_PTR(pOffset);
if (proc == MyProc)
continue; /* do not count myself */
if (proc->logRec.xrecoff == 0)
continue; /* do not count if not in a transaction */
if (proc->waitLock != NULL)
continue; /* do not count if blocked on a lock */
count++;
}
}
return count;
}
/*
* GetUndoRecPtr -- returns oldest PROC->logRec.
*/
XLogRecPtr GetUndoRecPtr(void);
XLogRecPtr
GetUndoRecPtr(void)
{

10
src/backend/utils/misc/guc.c
View File

@ -4,7 +4,7 @@
* Support for grand unified configuration scheme, including SET
* command, configuration file, and command line options.
*
* $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.30 2001/02/18 04:50:43 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.31 2001/02/26 00:50:07 tgl Exp $
*
* Copyright 2000 by PostgreSQL Global Development Group
* Written by Peter Eisentraut <peter_e@gmx.net>.
@ -41,6 +41,7 @@ extern int XLOGbuffers;
extern int XLOGfiles;
extern int XLOG_DEBUG;
extern int CommitDelay;
extern int CommitSiblings;
extern bool FixBTree;
@ -181,7 +182,7 @@ ConfigureNamesBool[] =
{"tcpip_socket", PGC_POSTMASTER, &NetServer, false},
{"ssl", PGC_POSTMASTER, &EnableSSL, false},
{"fsync", PGC_USERSET, &enableFsync, true},
{"fsync", PGC_SIGHUP, &enableFsync, true},
{"silent_mode", PGC_POSTMASTER, &SilentMode, false},
{"log_connections", PGC_SIGHUP, &Log_connections, false},
@ -279,7 +280,7 @@ ConfigureNamesInt[] =
0777, 0000, 0777},
{"checkpoint_timeout", PGC_POSTMASTER, &CheckPointTimeout,
300, 30, 1800},
300, 30, 3600},
{"wal_buffers", PGC_POSTMASTER, &XLOGbuffers,
8, 4, INT_MAX},
@ -293,6 +294,9 @@ ConfigureNamesInt[] =
{"commit_delay", PGC_USERSET, &CommitDelay,
0, 0, 100000},
{"commit_siblings", PGC_USERSET, &CommitSiblings,
5, 1, 1000},
{NULL, 0, NULL, 0, 0, 0}
};

3
src/backend/utils/misc/postgresql.conf.sample
View File

@ -109,7 +109,8 @@
#wal_files = 0 # range 0-64
#wal_debug = 0 # range 0-16
#commit_delay = 0 # range 0-100000
#checkpoint_timeout = 300 # range 30-1800
#commit_siblings = 5 # range 1-1000
#checkpoint_timeout = 300 # in seconds, range 30-3600
#

3
src/bin/psql/tab-complete.c
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@ -3,7 +3,7 @@
*
* Copyright 2000 by PostgreSQL Global Development Group
*
* $Header: /cvsroot/pgsql/src/bin/psql/tab-complete.c,v 1.26 2001/02/10 02:31:28 tgl Exp $
* $Header: /cvsroot/pgsql/src/bin/psql/tab-complete.c,v 1.27 2001/02/26 00:50:07 tgl Exp $
*/
/*----------------------------------------------------------------------
@ -241,6 +241,7 @@ psql_completion(char *text, int start, int end)
"debug_level",
"max_expr_depth",
"commit_delay",
"commit_siblings",
"effective_cache_size",
"random_page_cost",

7
src/include/access/xlog.h
View File

@ -3,7 +3,7 @@
*
* PostgreSQL transaction log manager
*
* $Header: /cvsroot/pgsql/src/include/access/xlog.h,v 1.17 2001/01/14 05:08:16 tgl Exp $
* $Header: /cvsroot/pgsql/src/include/access/xlog.h,v 1.18 2001/02/26 00:50:07 tgl Exp $
*/
#ifndef XLOG_H
#define XLOG_H
@ -146,4 +146,9 @@ extern void ShutdownXLOG(void);
extern void CreateCheckPoint(bool shutdown);
extern void SetThisStartUpID(void);
/* in storage/ipc/sinval.c, but don't want to declare in sinval.h because
* we'd have to include xlog.h into that ...
*/
extern XLogRecPtr GetUndoRecPtr(void);
#endif /* XLOG_H */

6
src/include/storage/proc.h
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: proc.h,v 1.39 2001/01/25 03:31:16 tgl Exp $
* $Id: proc.h,v 1.40 2001/02/26 00:50:08 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -50,6 +50,10 @@ struct proc
* were starting our xact: vacuum must not
* remove tuples deleted by xid >= xmin ! */
/* XLOG location of first XLOG record written by this backend's current
* transaction. If backend is not in a transaction or hasn't yet modified
* anything, logRec.xrecoff is zero.
*/
XLogRecPtr logRec;
/* Info about lock the process is currently waiting for, if any. */

4
src/include/storage/sinval.h
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: sinval.h,v 1.17 2001/01/24 19:43:28 momjian Exp $
* $Id: sinval.h,v 1.18 2001/02/26 00:50:08 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -30,6 +30,6 @@ extern void InvalidateSharedInvalid(void (*invalFunction) (),
extern bool DatabaseHasActiveBackends(Oid databaseId, bool ignoreMyself);
extern bool TransactionIdIsInProgress(TransactionId xid);
extern void GetXmaxRecent(TransactionId *XmaxRecent);
extern int CountActiveBackends(void);
#endif /* SINVAL_H */