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Commit5fa6c81

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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 parenta39e78b commit5fa6c81

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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
@@ -91,12 +91,18 @@ intsync_method = DEFAULT_SYNC_METHOD;
9191
intwal_level=WAL_LEVEL_MINIMAL;
9292
intCommitDelay=0;/* precommit delay in microseconds */
9393
intCommitSiblings=5;/* # concurrent xacts needed to sleep */
94-
intnum_xloginsert_locks=8;
9594

9695
#ifdefWAL_DEBUG
9796
boolXLOG_DEBUG= false;
9897
#endif
9998

99+
/*
100+
* Number of WAL insertion locks to use. A higher value allows more insertions
101+
* to happen concurrently, but adds some CPU overhead to flushing the WAL,
102+
* which needs to iterate all the locks.
103+
*/
104+
#defineNUM_XLOGINSERT_LOCKS 8
105+
100106
/*
101107
* XLOGfileslop is the maximum number of preallocated future XLOG segments.
102108
* When we are done with an old XLOG segment file, we will recycle it as a
@@ -1095,9 +1101,9 @@ begin:;
10951101
* inserter acquires an insertion lock. In addition to just indicating that
10961102
* an insertion is in progress, the lock tells others how far the inserter
10971103
* has progressed. There is a small fixed number of insertion locks,
1098-
* determined bythe num_xloginsert_locks GUC. When an inserter crosses a
1099-
*pageboundary, it updates the value stored in the lock to the how far it
1100-
*hasinserted, to allow the previous buffer to be flushed.
1104+
* determined byNUM_XLOGINSERT_LOCKS. When an inserter crosses a page
1105+
* boundary, it updates the value stored in the lock to the how far it has
1106+
* inserted, to allow the previous buffer to be flushed.
11011107
*
11021108
* Holding onto an insertion lock also protects RedoRecPtr and
11031109
* fullPageWrites from changing until the insertion is finished.
@@ -1578,7 +1584,7 @@ WALInsertLockAcquire(void)
15781584
staticintlockToTry=-1;
15791585

15801586
if (lockToTry==-1)
1581-
lockToTry=MyProc->pgprocno %num_xloginsert_locks;
1587+
lockToTry=MyProc->pgprocno %NUM_XLOGINSERT_LOCKS;
15821588
MyLockNo=lockToTry;
15831589

15841590
/*
@@ -1598,7 +1604,7 @@ WALInsertLockAcquire(void)
15981604
* than locks, it still helps to distribute the inserters evenly
15991605
* across the locks.
16001606
*/
1601-
lockToTry= (lockToTry+1) %num_xloginsert_locks;
1607+
lockToTry= (lockToTry+1) %NUM_XLOGINSERT_LOCKS;
16021608
}
16031609
}
16041610

@@ -1617,7 +1623,7 @@ WALInsertLockAcquireExclusive(void)
16171623
* than any real XLogRecPtr value, to make sure that no-one blocks waiting
16181624
* on those.
16191625
*/
1620-
for (i=0;i<num_xloginsert_locks-1;i++)
1626+
for (i=0;i<NUM_XLOGINSERT_LOCKS-1;i++)
16211627
{
16221628
LWLockAcquireWithVar(&WALInsertLocks[i].l.lock,
16231629
&WALInsertLocks[i].l.insertingAt,
@@ -1640,7 +1646,7 @@ WALInsertLockRelease(void)
16401646
{
16411647
inti;
16421648

1643-
for (i=0;i<num_xloginsert_locks;i++)
1649+
for (i=0;i<NUM_XLOGINSERT_LOCKS;i++)
16441650
LWLockRelease(&WALInsertLocks[i].l.lock);
16451651

16461652
holdingAllLocks= false;
@@ -1664,8 +1670,8 @@ WALInsertLockUpdateInsertingAt(XLogRecPtr insertingAt)
16641670
* We use the last lock to mark our actual position, see comments in
16651671
* WALInsertLockAcquireExclusive.
16661672
*/
1667-
LWLockUpdateVar(&WALInsertLocks[num_xloginsert_locks-1].l.lock,
1668-
&WALInsertLocks[num_xloginsert_locks-1].l.insertingAt,
1673+
LWLockUpdateVar(&WALInsertLocks[NUM_XLOGINSERT_LOCKS-1].l.lock,
1674+
&WALInsertLocks[NUM_XLOGINSERT_LOCKS-1].l.insertingAt,
16691675
insertingAt);
16701676
}
16711677
else
@@ -1732,7 +1738,7 @@ WaitXLogInsertionsToFinish(XLogRecPtr upto)
17321738
* out for any insertion that's still in progress.
17331739
*/
17341740
finishedUpto=reservedUpto;
1735-
for (i=0;i<num_xloginsert_locks;i++)
1741+
for (i=0;i<NUM_XLOGINSERT_LOCKS;i++)
17361742
{
17371743
XLogRecPtrinsertingat=InvalidXLogRecPtr;
17381744

@@ -4752,7 +4758,7 @@ XLOGShmemSize(void)
47524758
size=sizeof(XLogCtlData);
47534759

47544760
/* WAL insertion locks, plus alignment */
4755-
size=add_size(size,mul_size(sizeof(WALInsertLockPadded),num_xloginsert_locks+1));
4761+
size=add_size(size,mul_size(sizeof(WALInsertLockPadded),NUM_XLOGINSERT_LOCKS+1));
47564762
/* xlblocks array */
47574763
size=add_size(size,mul_size(sizeof(XLogRecPtr),XLOGbuffers));
47584764
/* extra alignment padding for XLOG I/O buffers */
@@ -4829,7 +4835,7 @@ XLOGShmemInit(void)
48294835
((uintptr_t)allocptr) %sizeof(WALInsertLockPadded);
48304836
WALInsertLocks=XLogCtl->Insert.WALInsertLocks=
48314837
(WALInsertLockPadded*)allocptr;
4832-
allocptr+=sizeof(WALInsertLockPadded)*num_xloginsert_locks;
4838+
allocptr+=sizeof(WALInsertLockPadded)*NUM_XLOGINSERT_LOCKS;
48334839

48344840
XLogCtl->Insert.WALInsertLockTrancheId=LWLockNewTrancheId();
48354841

@@ -4838,7 +4844,7 @@ XLOGShmemInit(void)
48384844
XLogCtl->Insert.WALInsertLockTranche.array_stride=sizeof(WALInsertLockPadded);
48394845

48404846
LWLockRegisterTranche(XLogCtl->Insert.WALInsertLockTrancheId,&XLogCtl->Insert.WALInsertLockTranche);
4841-
for (i=0;i<num_xloginsert_locks;i++)
4847+
for (i=0;i<NUM_XLOGINSERT_LOCKS;i++)
48424848
{
48434849
LWLockInitialize(&WALInsertLocks[i].l.lock,
48444850
XLogCtl->Insert.WALInsertLockTrancheId);

‎src/backend/utils/misc/guc.c

Lines changed: 0 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -2143,17 +2143,6 @@ static struct config_int ConfigureNamesInt[] =
21432143
NULL,NULL,NULL
21442144
},
21452145

2146-
{
2147-
{"xloginsert_locks",PGC_POSTMASTER,WAL_SETTINGS,
2148-
gettext_noop("Sets the number of locks used for concurrent xlog insertions."),
2149-
NULL,
2150-
GUC_NOT_IN_SAMPLE
2151-
},
2152-
&num_xloginsert_locks,
2153-
8,1,1000,
2154-
NULL,NULL,NULL
2155-
},
2156-
21572146
{
21582147
/* see max_connections */
21592148
{"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
@@ -194,7 +194,6 @@ extern bool EnableHotStandby;
194194
externboolfullPageWrites;
195195
externboolwal_log_hints;
196196
externboollog_checkpoints;
197-
externintnum_xloginsert_locks;
198197

199198
/* WAL levels */
200199
typedefenumWalLevel

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