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Commit75848bc

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snapshot scalability: Move delayChkpt from PGXACT to PGPROC.
The goal of separating hotly accessed per-backend data from PGPROCinto PGXACT is to make accesses fast (GetSnapshotData() inparticular). But delayChkpt is not actually accessed frequently; onlywhen starting a checkpoint. As it is frequently modified (multipletimes in the course of a single transaction), storing it in the samecacheline as hotly accessed data unnecessarily dirties a contendedcacheline.Therefore move delayChkpt to PGPROC.This is part of a larger series of patches intending to improveGetSnapshotData() scalability. It is committed and pushed separately,as it is independently beneficial (small but measurable win, limitedby the other frequent modifications of PGXACT).Author: Andres FreundReviewed-By: Robert Haas, Thomas Munro, David RowleyDiscussion:https://postgr.es/m/20200301083601.ews6hz5dduc3w2se@alap3.anarazel.de
1 parent2b88fdd commit75848bc

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8 files changed

+23
-25
lines changed

8 files changed

+23
-25
lines changed

‎src/backend/access/transam/multixact.c‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -3058,8 +3058,8 @@ TruncateMultiXact(MultiXactId newOldestMulti, Oid newOldestMultiDB)
30583058
* crash/basebackup, even though the state of the data directory would
30593059
* require it.
30603060
*/
3061-
Assert(!MyPgXact->delayChkpt);
3062-
MyPgXact->delayChkpt= true;
3061+
Assert(!MyProc->delayChkpt);
3062+
MyProc->delayChkpt= true;
30633063

30643064
/* WAL log truncation */
30653065
WriteMTruncateXlogRec(newOldestMultiDB,
@@ -3085,7 +3085,7 @@ TruncateMultiXact(MultiXactId newOldestMulti, Oid newOldestMultiDB)
30853085
/* Then offsets */
30863086
PerformOffsetsTruncation(oldestMulti,newOldestMulti);
30873087

3088-
MyPgXact->delayChkpt= false;
3088+
MyProc->delayChkpt= false;
30893089

30903090
END_CRIT_SECTION();
30913091
LWLockRelease(MultiXactTruncationLock);

‎src/backend/access/transam/twophase.c‎

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -465,7 +465,7 @@ MarkAsPreparingGuts(GlobalTransaction gxact, TransactionId xid, const char *gid,
465465
proc->lxid= (LocalTransactionId)xid;
466466
pgxact->xid=xid;
467467
pgxact->xmin=InvalidTransactionId;
468-
pgxact->delayChkpt= false;
468+
proc->delayChkpt= false;
469469
pgxact->vacuumFlags=0;
470470
proc->pid=0;
471471
proc->backendId=InvalidBackendId;
@@ -1114,7 +1114,7 @@ EndPrepare(GlobalTransaction gxact)
11141114

11151115
START_CRIT_SECTION();
11161116

1117-
MyPgXact->delayChkpt= true;
1117+
MyProc->delayChkpt= true;
11181118

11191119
XLogBeginInsert();
11201120
for (record=records.head;record!=NULL;record=record->next)
@@ -1157,7 +1157,7 @@ EndPrepare(GlobalTransaction gxact)
11571157
* checkpoint starting after this will certainly see the gxact as a
11581158
* candidate for fsyncing.
11591159
*/
1160-
MyPgXact->delayChkpt= false;
1160+
MyProc->delayChkpt= false;
11611161

11621162
/*
11631163
* Remember that we have this GlobalTransaction entry locked for us. If
@@ -2204,7 +2204,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
22042204
START_CRIT_SECTION();
22052205

22062206
/* See notes in RecordTransactionCommit */
2207-
MyPgXact->delayChkpt= true;
2207+
MyProc->delayChkpt= true;
22082208

22092209
/*
22102210
* Emit the XLOG commit record. Note that we mark 2PC commits as
@@ -2252,7 +2252,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
22522252
TransactionIdCommitTree(xid,nchildren,children);
22532253

22542254
/* Checkpoint can proceed now */
2255-
MyPgXact->delayChkpt= false;
2255+
MyProc->delayChkpt= false;
22562256

22572257
END_CRIT_SECTION();
22582258

‎src/backend/access/transam/xact.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1307,7 +1307,7 @@ RecordTransactionCommit(void)
13071307
* a bit fuzzy, but it doesn't matter.
13081308
*/
13091309
START_CRIT_SECTION();
1310-
MyPgXact->delayChkpt= true;
1310+
MyProc->delayChkpt= true;
13111311

13121312
SetCurrentTransactionStopTimestamp();
13131313

@@ -1408,7 +1408,7 @@ RecordTransactionCommit(void)
14081408
*/
14091409
if (markXidCommitted)
14101410
{
1411-
MyPgXact->delayChkpt= false;
1411+
MyProc->delayChkpt= false;
14121412
END_CRIT_SECTION();
14131413
}
14141414

‎src/backend/access/transam/xloginsert.c‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -904,7 +904,7 @@ XLogSaveBufferForHint(Buffer buffer, bool buffer_std)
904904
/*
905905
* Ensure no checkpoint can change our view of RedoRecPtr.
906906
*/
907-
Assert(MyPgXact->delayChkpt);
907+
Assert(MyProc->delayChkpt);
908908

909909
/*
910910
* Update RedoRecPtr so that we can make the right decision

‎src/backend/storage/buffer/bufmgr.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3587,7 +3587,7 @@ MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
35873587
* essential that CreateCheckpoint waits for virtual transactions
35883588
* rather than full transactionids.
35893589
*/
3590-
MyPgXact->delayChkpt=delayChkpt= true;
3590+
MyProc->delayChkpt=delayChkpt= true;
35913591
lsn=XLogSaveBufferForHint(buffer,buffer_std);
35923592
}
35933593

@@ -3620,7 +3620,7 @@ MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
36203620
UnlockBufHdr(bufHdr,buf_state);
36213621

36223622
if (delayChkpt)
3623-
MyPgXact->delayChkpt= false;
3623+
MyProc->delayChkpt= false;
36243624

36253625
if (dirtied)
36263626
{

‎src/backend/storage/ipc/procarray.c‎

Lines changed: 6 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -436,7 +436,7 @@ ProcArrayEndTransaction(PGPROC *proc, TransactionId latestXid)
436436
pgxact->xmin=InvalidTransactionId;
437437
/* must be cleared with xid/xmin: */
438438
pgxact->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
439-
pgxact->delayChkpt= false;/* be sure this is cleared in abort */
439+
proc->delayChkpt= false;/* be sure this is cleared in abort */
440440
proc->recoveryConflictPending= false;
441441

442442
Assert(pgxact->nxids==0);
@@ -458,7 +458,7 @@ ProcArrayEndTransactionInternal(PGPROC *proc, PGXACT *pgxact,
458458
pgxact->xmin=InvalidTransactionId;
459459
/* must be cleared with xid/xmin: */
460460
pgxact->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
461-
pgxact->delayChkpt= false;/* be sure this is cleared in abort */
461+
proc->delayChkpt= false;/* be sure this is cleared in abort */
462462
proc->recoveryConflictPending= false;
463463

464464
/* Clear the subtransaction-XID cache too while holding the lock */
@@ -616,7 +616,7 @@ ProcArrayClearTransaction(PGPROC *proc)
616616

617617
/* redundant, but just in case */
618618
pgxact->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
619-
pgxact->delayChkpt= false;
619+
proc->delayChkpt= false;
620620

621621
/* Clear the subtransaction-XID cache too */
622622
pgxact->nxids=0;
@@ -2257,7 +2257,7 @@ GetOldestSafeDecodingTransactionId(bool catalogOnly)
22572257
* delaying checkpoint because they have critical actions in progress.
22582258
*
22592259
* Constructs an array of VXIDs of transactions that are currently in commit
2260-
* critical sections, as shown by having delayChkpt set in theirPGXACT.
2260+
* critical sections, as shown by having delayChkpt set in theirPGPROC.
22612261
*
22622262
* Returns a palloc'd array that should be freed by the caller.
22632263
* *nvxids is the number of valid entries.
@@ -2288,9 +2288,8 @@ GetVirtualXIDsDelayingChkpt(int *nvxids)
22882288
{
22892289
intpgprocno=arrayP->pgprocnos[index];
22902290
PGPROC*proc=&allProcs[pgprocno];
2291-
PGXACT*pgxact=&allPgXact[pgprocno];
22922291

2293-
if (pgxact->delayChkpt)
2292+
if (proc->delayChkpt)
22942293
{
22952294
VirtualTransactionIdvxid;
22962295

@@ -2328,12 +2327,11 @@ HaveVirtualXIDsDelayingChkpt(VirtualTransactionId *vxids, int nvxids)
23282327
{
23292328
intpgprocno=arrayP->pgprocnos[index];
23302329
PGPROC*proc=&allProcs[pgprocno];
2331-
PGXACT*pgxact=&allPgXact[pgprocno];
23322330
VirtualTransactionIdvxid;
23332331

23342332
GET_VXID_FROM_PGPROC(vxid,*proc);
23352333

2336-
if (pgxact->delayChkpt&&VirtualTransactionIdIsValid(vxid))
2334+
if (proc->delayChkpt&&VirtualTransactionIdIsValid(vxid))
23372335
{
23382336
inti;
23392337

‎src/backend/storage/lmgr/proc.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -397,7 +397,7 @@ InitProcess(void)
397397
MyProc->roleId=InvalidOid;
398398
MyProc->tempNamespaceId=InvalidOid;
399399
MyProc->isBackgroundWorker=IsBackgroundWorker;
400-
MyPgXact->delayChkpt= false;
400+
MyProc->delayChkpt= false;
401401
MyPgXact->vacuumFlags=0;
402402
/* NB -- autovac launcher intentionally does not set IS_AUTOVACUUM */
403403
if (IsAutoVacuumWorkerProcess())
@@ -579,7 +579,7 @@ InitAuxiliaryProcess(void)
579579
MyProc->roleId=InvalidOid;
580580
MyProc->tempNamespaceId=InvalidOid;
581581
MyProc->isBackgroundWorker=IsBackgroundWorker;
582-
MyPgXact->delayChkpt= false;
582+
MyProc->delayChkpt= false;
583583
MyPgXact->vacuumFlags=0;
584584
MyProc->lwWaiting= false;
585585
MyProc->lwWaitMode=0;

‎src/include/storage/proc.h‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -142,6 +142,8 @@ struct PGPROC
142142
LOCKMASKheldLocks;/* bitmask for lock types already held on this
143143
* lock object by this backend */
144144

145+
booldelayChkpt;/* true if this proc delays checkpoint start */
146+
145147
/*
146148
* Info to allow us to wait for synchronous replication, if needed.
147149
* waitLSN is InvalidXLogRecPtr if not waiting; set only by user backend.
@@ -232,8 +234,6 @@ typedef struct PGXACT
232234

233235
uint8vacuumFlags;/* vacuum-related flags, see above */
234236
booloverflowed;
235-
booldelayChkpt;/* true if this proc delays checkpoint start;
236-
* previously called InCommit */
237237

238238
uint8nxids;
239239
}PGXACT;

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