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Commitfc0acf4

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Remove num_xloginsert_locks GUC, replace with a #define
I left the GUC in place for the beta period, so that people could experimentwith different values. No-one's come up with any data that a different valuewould be better under some circumstances, so rather than try to document tousers what the GUC, let's just hard-code the current value, 8.
1 parente14ed8e commitfc0acf4

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3 files changed

+20
-26
lines changed

3 files changed

+20
-26
lines changed

‎src/backend/access/transam/xlog.c‎

Lines changed: 20 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -90,12 +90,18 @@ intsync_method = DEFAULT_SYNC_METHOD;
9090
intwal_level=WAL_LEVEL_MINIMAL;
9191
intCommitDelay=0;/* precommit delay in microseconds */
9292
intCommitSiblings=5;/* # concurrent xacts needed to sleep */
93-
intnum_xloginsert_locks=8;
9493

9594
#ifdefWAL_DEBUG
9695
boolXLOG_DEBUG= false;
9796
#endif
9897

98+
/*
99+
* Number of WAL insertion locks to use. A higher value allows more insertions
100+
* to happen concurrently, but adds some CPU overhead to flushing the WAL,
101+
* which needs to iterate all the locks.
102+
*/
103+
#defineNUM_XLOGINSERT_LOCKS 8
104+
99105
/*
100106
* XLOGfileslop is the maximum number of preallocated future XLOG segments.
101107
* When we are done with an old XLOG segment file, we will recycle it as a
@@ -1089,9 +1095,9 @@ begin:;
10891095
* inserter acquires an insertion lock. In addition to just indicating that
10901096
* an insertion is in progress, the lock tells others how far the inserter
10911097
* has progressed. There is a small fixed number of insertion locks,
1092-
* determined bythe num_xloginsert_locks GUC. When an inserter crosses a
1093-
*pageboundary, it updates the value stored in the lock to the how far it
1094-
*hasinserted, to allow the previous buffer to be flushed.
1098+
* determined byNUM_XLOGINSERT_LOCKS. When an inserter crosses a page
1099+
* boundary, it updates the value stored in the lock to the how far it has
1100+
* inserted, to allow the previous buffer to be flushed.
10951101
*
10961102
* Holding onto an insertion lock also protects RedoRecPtr and
10971103
* fullPageWrites from changing until the insertion is finished.
@@ -1572,7 +1578,7 @@ WALInsertLockAcquire(void)
15721578
staticintlockToTry=-1;
15731579

15741580
if (lockToTry==-1)
1575-
lockToTry=MyProc->pgprocno %num_xloginsert_locks;
1581+
lockToTry=MyProc->pgprocno %NUM_XLOGINSERT_LOCKS;
15761582
MyLockNo=lockToTry;
15771583

15781584
/*
@@ -1592,7 +1598,7 @@ WALInsertLockAcquire(void)
15921598
* than locks, it still helps to distribute the inserters evenly
15931599
* across the locks.
15941600
*/
1595-
lockToTry= (lockToTry+1) %num_xloginsert_locks;
1601+
lockToTry= (lockToTry+1) %NUM_XLOGINSERT_LOCKS;
15961602
}
15971603
}
15981604

@@ -1611,7 +1617,7 @@ WALInsertLockAcquireExclusive(void)
16111617
* than any real XLogRecPtr value, to make sure that no-one blocks waiting
16121618
* on those.
16131619
*/
1614-
for (i=0;i<num_xloginsert_locks-1;i++)
1620+
for (i=0;i<NUM_XLOGINSERT_LOCKS-1;i++)
16151621
{
16161622
LWLockAcquireWithVar(&WALInsertLocks[i].l.lock,
16171623
&WALInsertLocks[i].l.insertingAt,
@@ -1634,7 +1640,7 @@ WALInsertLockRelease(void)
16341640
{
16351641
inti;
16361642

1637-
for (i=0;i<num_xloginsert_locks;i++)
1643+
for (i=0;i<NUM_XLOGINSERT_LOCKS;i++)
16381644
LWLockRelease(&WALInsertLocks[i].l.lock);
16391645

16401646
holdingAllLocks= false;
@@ -1658,8 +1664,8 @@ WALInsertLockUpdateInsertingAt(XLogRecPtr insertingAt)
16581664
* We use the last lock to mark our actual position, see comments in
16591665
* WALInsertLockAcquireExclusive.
16601666
*/
1661-
LWLockUpdateVar(&WALInsertLocks[num_xloginsert_locks-1].l.lock,
1662-
&WALInsertLocks[num_xloginsert_locks-1].l.insertingAt,
1667+
LWLockUpdateVar(&WALInsertLocks[NUM_XLOGINSERT_LOCKS-1].l.lock,
1668+
&WALInsertLocks[NUM_XLOGINSERT_LOCKS-1].l.insertingAt,
16631669
insertingAt);
16641670
}
16651671
else
@@ -1726,7 +1732,7 @@ WaitXLogInsertionsToFinish(XLogRecPtr upto)
17261732
* out for any insertion that's still in progress.
17271733
*/
17281734
finishedUpto=reservedUpto;
1729-
for (i=0;i<num_xloginsert_locks;i++)
1735+
for (i=0;i<NUM_XLOGINSERT_LOCKS;i++)
17301736
{
17311737
XLogRecPtrinsertingat=InvalidXLogRecPtr;
17321738

@@ -4781,7 +4787,7 @@ XLOGShmemSize(void)
47814787
size=sizeof(XLogCtlData);
47824788

47834789
/* WAL insertion locks, plus alignment */
4784-
size=add_size(size,mul_size(sizeof(WALInsertLockPadded),num_xloginsert_locks+1));
4790+
size=add_size(size,mul_size(sizeof(WALInsertLockPadded),NUM_XLOGINSERT_LOCKS+1));
47854791
/* xlblocks array */
47864792
size=add_size(size,mul_size(sizeof(XLogRecPtr),XLOGbuffers));
47874793
/* extra alignment padding for XLOG I/O buffers */
@@ -4840,7 +4846,7 @@ XLOGShmemInit(void)
48404846
((uintptr_t)allocptr) %sizeof(WALInsertLockPadded);
48414847
WALInsertLocks=XLogCtl->Insert.WALInsertLocks=
48424848
(WALInsertLockPadded*)allocptr;
4843-
allocptr+=sizeof(WALInsertLockPadded)*num_xloginsert_locks;
4849+
allocptr+=sizeof(WALInsertLockPadded)*NUM_XLOGINSERT_LOCKS;
48444850

48454851
XLogCtl->Insert.WALInsertLockTrancheId=LWLockNewTrancheId();
48464852

@@ -4849,7 +4855,7 @@ XLOGShmemInit(void)
48494855
XLogCtl->Insert.WALInsertLockTranche.array_stride=sizeof(WALInsertLockPadded);
48504856

48514857
LWLockRegisterTranche(XLogCtl->Insert.WALInsertLockTrancheId,&XLogCtl->Insert.WALInsertLockTranche);
4852-
for (i=0;i<num_xloginsert_locks;i++)
4858+
for (i=0;i<NUM_XLOGINSERT_LOCKS;i++)
48534859
{
48544860
LWLockInitialize(&WALInsertLocks[i].l.lock,
48554861
XLogCtl->Insert.WALInsertLockTrancheId);

‎src/backend/utils/misc/guc.c‎

Lines changed: 0 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -2119,17 +2119,6 @@ static struct config_int ConfigureNamesInt[] =
21192119
NULL,NULL,NULL
21202120
},
21212121

2122-
{
2123-
{"xloginsert_locks",PGC_POSTMASTER,WAL_SETTINGS,
2124-
gettext_noop("Sets the number of locks used for concurrent xlog insertions."),
2125-
NULL,
2126-
GUC_NOT_IN_SAMPLE
2127-
},
2128-
&num_xloginsert_locks,
2129-
8,1,1000,
2130-
NULL,NULL,NULL
2131-
},
2132-
21332122
{
21342123
/* see max_connections */
21352124
{"max_wal_senders",PGC_POSTMASTER,REPLICATION_SENDING,

‎src/include/access/xlog.h‎

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -192,7 +192,6 @@ extern bool EnableHotStandby;
192192
externboolfullPageWrites;
193193
externboolwal_log_hints;
194194
externboollog_checkpoints;
195-
externintnum_xloginsert_locks;
196195

197196
/* WAL levels */
198197
typedefenumWalLevel

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