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Commited0b409

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committed
Move "hot" members of PGPROC into a separate PGXACT array.
This speeds up snapshot-taking and reduces ProcArrayLock contention.Also, the PGPROC (and PGXACT) structures used by two-phase commit arenow allocated as part of the main array, rather than in a separatearray, and we keep ProcArray sorted in pointer order. These changesare intended to minimize the number of cache lines that must be pulledin to take a snapshot, and testing shows a substantial increase inperformance on both read and write workloads at high concurrencies.Pavan Deolasee, Heikki Linnakangas, Robert Haas
1 parent9ed439a commited0b409

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14 files changed

+356
-208
lines changed

14 files changed

+356
-208
lines changed

‎src/backend/access/transam/twophase.c‎

Lines changed: 69 additions & 46 deletions
Original file line numberDiff line numberDiff line change
@@ -113,7 +113,8 @@ intmax_prepared_xacts = 0;
113113

114114
typedefstructGlobalTransactionData
115115
{
116-
PGPROCproc;/* dummy proc */
116+
GlobalTransactionnext;
117+
intpgprocno;/* dummy proc */
117118
BackendIddummyBackendId;/* similar to backend id for backends */
118119
TimestampTzprepared_at;/* time of preparation */
119120
XLogRecPtrprepare_lsn;/* XLOG offset of prepare record */
@@ -207,7 +208,8 @@ TwoPhaseShmemInit(void)
207208
sizeof(GlobalTransaction)*max_prepared_xacts));
208209
for (i=0;i<max_prepared_xacts;i++)
209210
{
210-
gxacts[i].proc.links.next= (SHM_QUEUE*)TwoPhaseState->freeGXacts;
211+
gxacts[i].pgprocno=PreparedXactProcs[i].pgprocno;
212+
gxacts[i].next=TwoPhaseState->freeGXacts;
211213
TwoPhaseState->freeGXacts=&gxacts[i];
212214

213215
/*
@@ -243,6 +245,8 @@ MarkAsPreparing(TransactionId xid, const char *gid,
243245
TimestampTzprepared_at,Oidowner,Oiddatabaseid)
244246
{
245247
GlobalTransactiongxact;
248+
PGPROC*proc;
249+
PGXACT*pgxact;
246250
inti;
247251

248252
if (strlen(gid) >=GIDSIZE)
@@ -274,7 +278,7 @@ MarkAsPreparing(TransactionId xid, const char *gid,
274278
TwoPhaseState->numPrepXacts--;
275279
TwoPhaseState->prepXacts[i]=TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts];
276280
/* and put it back in the freelist */
277-
gxact->proc.links.next= (SHM_QUEUE*)TwoPhaseState->freeGXacts;
281+
gxact->next=TwoPhaseState->freeGXacts;
278282
TwoPhaseState->freeGXacts=gxact;
279283
/* Back up index count too, so we don't miss scanning one */
280284
i--;
@@ -302,32 +306,36 @@ MarkAsPreparing(TransactionId xid, const char *gid,
302306
errhint("Increase max_prepared_transactions (currently %d).",
303307
max_prepared_xacts)));
304308
gxact=TwoPhaseState->freeGXacts;
305-
TwoPhaseState->freeGXacts= (GlobalTransaction)gxact->proc.links.next;
309+
TwoPhaseState->freeGXacts= (GlobalTransaction)gxact->next;
306310

307-
/* Initialize it */
308-
MemSet(&gxact->proc,0,sizeof(PGPROC));
309-
SHMQueueElemInit(&(gxact->proc.links));
310-
gxact->proc.waitStatus=STATUS_OK;
311+
proc=&ProcGlobal->allProcs[gxact->pgprocno];
312+
pgxact=&ProcGlobal->allPgXact[gxact->pgprocno];
313+
314+
/* Initialize the PGPROC entry */
315+
MemSet(proc,0,sizeof(PGPROC));
316+
proc->pgprocno=gxact->pgprocno;
317+
SHMQueueElemInit(&(proc->links));
318+
proc->waitStatus=STATUS_OK;
311319
/* We set up the gxact's VXID as InvalidBackendId/XID */
312-
gxact->proc.lxid= (LocalTransactionId)xid;
313-
gxact->proc.xid=xid;
314-
gxact->proc.xmin=InvalidTransactionId;
315-
gxact->proc.pid=0;
316-
gxact->proc.backendId=InvalidBackendId;
317-
gxact->proc.databaseId=databaseid;
318-
gxact->proc.roleId=owner;
319-
gxact->proc.inCommit=false;
320-
gxact->proc.vacuumFlags=0;
321-
gxact->proc.lwWaiting= false;
322-
gxact->proc.lwExclusive= false;
323-
gxact->proc.lwWaitLink=NULL;
324-
gxact->proc.waitLock=NULL;
325-
gxact->proc.waitProcLock=NULL;
320+
proc->lxid= (LocalTransactionId)xid;
321+
pgxact->xid=xid;
322+
pgxact->xmin=InvalidTransactionId;
323+
pgxact->inCommit=false;
324+
pgxact->vacuumFlags=0;
325+
proc->pid=0;
326+
proc->backendId=InvalidBackendId;
327+
proc->databaseId=databaseid;
328+
proc->roleId=owner;
329+
proc->lwWaiting= false;
330+
proc->lwExclusive= false;
331+
proc->lwWaitLink=NULL;
332+
proc->waitLock=NULL;
333+
proc->waitProcLock=NULL;
326334
for (i=0;i<NUM_LOCK_PARTITIONS;i++)
327-
SHMQueueInit(&(gxact->proc.myProcLocks[i]));
335+
SHMQueueInit(&(proc->myProcLocks[i]));
328336
/* subxid data must be filled later by GXactLoadSubxactData */
329-
gxact->proc.subxids.overflowed= false;
330-
gxact->proc.subxids.nxids=0;
337+
pgxact->overflowed= false;
338+
pgxact->nxids=0;
331339

332340
gxact->prepared_at=prepared_at;
333341
/* initialize LSN to 0 (start of WAL) */
@@ -358,17 +366,19 @@ static void
358366
GXactLoadSubxactData(GlobalTransactiongxact,intnsubxacts,
359367
TransactionId*children)
360368
{
369+
PGPROC*proc=&ProcGlobal->allProcs[gxact->pgprocno];
370+
PGXACT*pgxact=&ProcGlobal->allPgXact[gxact->pgprocno];
361371
/* We need no extra lock since the GXACT isn't valid yet */
362372
if (nsubxacts>PGPROC_MAX_CACHED_SUBXIDS)
363373
{
364-
gxact->proc.subxids.overflowed= true;
374+
pgxact->overflowed= true;
365375
nsubxacts=PGPROC_MAX_CACHED_SUBXIDS;
366376
}
367377
if (nsubxacts>0)
368378
{
369-
memcpy(gxact->proc.subxids.xids,children,
379+
memcpy(proc->subxids.xids,children,
370380
nsubxacts*sizeof(TransactionId));
371-
gxact->proc.subxids.nxids=nsubxacts;
381+
pgxact->nxids=nsubxacts;
372382
}
373383
}
374384

@@ -389,7 +399,7 @@ MarkAsPrepared(GlobalTransaction gxact)
389399
* Put it into the global ProcArray so TransactionIdIsInProgress considers
390400
* the XID as still running.
391401
*/
392-
ProcArrayAdd(&gxact->proc);
402+
ProcArrayAdd(&ProcGlobal->allProcs[gxact->pgprocno]);
393403
}
394404

395405
/*
@@ -406,6 +416,7 @@ LockGXact(const char *gid, Oid user)
406416
for (i=0;i<TwoPhaseState->numPrepXacts;i++)
407417
{
408418
GlobalTransactiongxact=TwoPhaseState->prepXacts[i];
419+
PGPROC*proc=&ProcGlobal->allProcs[gxact->pgprocno];
409420

410421
/* Ignore not-yet-valid GIDs */
411422
if (!gxact->valid)
@@ -436,7 +447,7 @@ LockGXact(const char *gid, Oid user)
436447
* there may be some other issues as well.Hence disallow until
437448
* someone gets motivated to make it work.
438449
*/
439-
if (MyDatabaseId!=gxact->proc.databaseId)
450+
if (MyDatabaseId!=proc->databaseId)
440451
ereport(ERROR,
441452
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
442453
errmsg("prepared transaction belongs to another database"),
@@ -483,7 +494,7 @@ RemoveGXact(GlobalTransaction gxact)
483494
TwoPhaseState->prepXacts[i]=TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts];
484495

485496
/* and put it back in the freelist */
486-
gxact->proc.links.next= (SHM_QUEUE*)TwoPhaseState->freeGXacts;
497+
gxact->next=TwoPhaseState->freeGXacts;
487498
TwoPhaseState->freeGXacts=gxact;
488499

489500
LWLockRelease(TwoPhaseStateLock);
@@ -518,8 +529,9 @@ TransactionIdIsPrepared(TransactionId xid)
518529
for (i=0;i<TwoPhaseState->numPrepXacts;i++)
519530
{
520531
GlobalTransactiongxact=TwoPhaseState->prepXacts[i];
532+
PGXACT*pgxact=&ProcGlobal->allPgXact[gxact->pgprocno];
521533

522-
if (gxact->valid&&gxact->proc.xid==xid)
534+
if (gxact->valid&&pgxact->xid==xid)
523535
{
524536
result= true;
525537
break;
@@ -642,6 +654,8 @@ pg_prepared_xact(PG_FUNCTION_ARGS)
642654
while (status->array!=NULL&&status->currIdx<status->ngxacts)
643655
{
644656
GlobalTransactiongxact=&status->array[status->currIdx++];
657+
PGPROC*proc=&ProcGlobal->allProcs[gxact->pgprocno];
658+
PGXACT*pgxact=&ProcGlobal->allPgXact[gxact->pgprocno];
645659
Datumvalues[5];
646660
boolnulls[5];
647661
HeapTupletuple;
@@ -656,11 +670,11 @@ pg_prepared_xact(PG_FUNCTION_ARGS)
656670
MemSet(values,0,sizeof(values));
657671
MemSet(nulls,0,sizeof(nulls));
658672

659-
values[0]=TransactionIdGetDatum(gxact->proc.xid);
673+
values[0]=TransactionIdGetDatum(pgxact->xid);
660674
values[1]=CStringGetTextDatum(gxact->gid);
661675
values[2]=TimestampTzGetDatum(gxact->prepared_at);
662676
values[3]=ObjectIdGetDatum(gxact->owner);
663-
values[4]=ObjectIdGetDatum(gxact->proc.databaseId);
677+
values[4]=ObjectIdGetDatum(proc->databaseId);
664678

665679
tuple=heap_form_tuple(funcctx->tuple_desc,values,nulls);
666680
result=HeapTupleGetDatum(tuple);
@@ -711,10 +725,11 @@ TwoPhaseGetDummyProc(TransactionId xid)
711725
for (i=0;i<TwoPhaseState->numPrepXacts;i++)
712726
{
713727
GlobalTransactiongxact=TwoPhaseState->prepXacts[i];
728+
PGXACT*pgxact=&ProcGlobal->allPgXact[gxact->pgprocno];
714729

715-
if (gxact->proc.xid==xid)
730+
if (pgxact->xid==xid)
716731
{
717-
result=&gxact->proc;
732+
result=&ProcGlobal->allProcs[gxact->pgprocno];
718733
break;
719734
}
720735
}
@@ -841,7 +856,9 @@ save_state_data(const void *data, uint32 len)
841856
void
842857
StartPrepare(GlobalTransactiongxact)
843858
{
844-
TransactionIdxid=gxact->proc.xid;
859+
PGPROC*proc=&ProcGlobal->allProcs[gxact->pgprocno];
860+
PGXACT*pgxact=&ProcGlobal->allPgXact[gxact->pgprocno];
861+
TransactionIdxid=pgxact->xid;
845862
TwoPhaseFileHeaderhdr;
846863
TransactionId*children;
847864
RelFileNode*commitrels;
@@ -865,7 +882,7 @@ StartPrepare(GlobalTransaction gxact)
865882
hdr.magic=TWOPHASE_MAGIC;
866883
hdr.total_len=0;/* EndPrepare will fill this in */
867884
hdr.xid=xid;
868-
hdr.database=gxact->proc.databaseId;
885+
hdr.database=proc->databaseId;
869886
hdr.prepared_at=gxact->prepared_at;
870887
hdr.owner=gxact->owner;
871888
hdr.nsubxacts=xactGetCommittedChildren(&children);
@@ -913,7 +930,8 @@ StartPrepare(GlobalTransaction gxact)
913930
void
914931
EndPrepare(GlobalTransactiongxact)
915932
{
916-
TransactionIdxid=gxact->proc.xid;
933+
PGXACT*pgxact=&ProcGlobal->allPgXact[gxact->pgprocno];
934+
TransactionIdxid=pgxact->xid;
917935
TwoPhaseFileHeader*hdr;
918936
charpath[MAXPGPATH];
919937
XLogRecData*record;
@@ -1021,7 +1039,7 @@ EndPrepare(GlobalTransaction gxact)
10211039
*/
10221040
START_CRIT_SECTION();
10231041

1024-
MyProc->inCommit= true;
1042+
MyPgXact->inCommit= true;
10251043

10261044
gxact->prepare_lsn=XLogInsert(RM_XACT_ID,XLOG_XACT_PREPARE,
10271045
records.head);
@@ -1069,7 +1087,7 @@ EndPrepare(GlobalTransaction gxact)
10691087
* checkpoint starting after this will certainly see the gxact as a
10701088
* candidate for fsyncing.
10711089
*/
1072-
MyProc->inCommit= false;
1090+
MyPgXact->inCommit= false;
10731091

10741092
END_CRIT_SECTION();
10751093

@@ -1242,6 +1260,8 @@ void
12421260
FinishPreparedTransaction(constchar*gid,boolisCommit)
12431261
{
12441262
GlobalTransactiongxact;
1263+
PGPROC*proc;
1264+
PGXACT*pgxact;
12451265
TransactionIdxid;
12461266
char*buf;
12471267
char*bufptr;
@@ -1260,7 +1280,9 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
12601280
* try to commit the same GID at once.
12611281
*/
12621282
gxact=LockGXact(gid,GetUserId());
1263-
xid=gxact->proc.xid;
1283+
proc=&ProcGlobal->allProcs[gxact->pgprocno];
1284+
pgxact=&ProcGlobal->allPgXact[gxact->pgprocno];
1285+
xid=pgxact->xid;
12641286

12651287
/*
12661288
* Read and validate the state file
@@ -1309,7 +1331,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
13091331
hdr->nsubxacts,children,
13101332
hdr->nabortrels,abortrels);
13111333

1312-
ProcArrayRemove(&gxact->proc,latestXid);
1334+
ProcArrayRemove(proc,latestXid);
13131335

13141336
/*
13151337
* In case we fail while running the callbacks, mark the gxact invalid so
@@ -1540,10 +1562,11 @@ CheckPointTwoPhase(XLogRecPtr redo_horizon)
15401562
for (i=0;i<TwoPhaseState->numPrepXacts;i++)
15411563
{
15421564
GlobalTransactiongxact=TwoPhaseState->prepXacts[i];
1565+
PGXACT*pgxact=&ProcGlobal->allPgXact[gxact->pgprocno];
15431566

15441567
if (gxact->valid&&
15451568
XLByteLE(gxact->prepare_lsn,redo_horizon))
1546-
xids[nxids++]=gxact->proc.xid;
1569+
xids[nxids++]=pgxact->xid;
15471570
}
15481571

15491572
LWLockRelease(TwoPhaseStateLock);
@@ -1972,7 +1995,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
19721995
START_CRIT_SECTION();
19731996

19741997
/* See notes in RecordTransactionCommit */
1975-
MyProc->inCommit= true;
1998+
MyPgXact->inCommit= true;
19761999

19772000
/* Emit the XLOG commit record */
19782001
xlrec.xid=xid;
@@ -2037,7 +2060,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
20372060
TransactionIdCommitTree(xid,nchildren,children);
20382061

20392062
/* Checkpoint can proceed now */
2040-
MyProc->inCommit= false;
2063+
MyPgXact->inCommit= false;
20412064

20422065
END_CRIT_SECTION();
20432066

‎src/backend/access/transam/varsup.c‎

Lines changed: 6 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -54,7 +54,7 @@ GetNewTransactionId(bool isSubXact)
5454
if (IsBootstrapProcessingMode())
5555
{
5656
Assert(!isSubXact);
57-
MyProc->xid=BootstrapTransactionId;
57+
MyPgXact->xid=BootstrapTransactionId;
5858
returnBootstrapTransactionId;
5959
}
6060

@@ -208,20 +208,21 @@ GetNewTransactionId(bool isSubXact)
208208
* TransactionId and int fetch/store are atomic.
209209
*/
210210
volatilePGPROC*myproc=MyProc;
211+
volatilePGXACT*mypgxact=MyPgXact;
211212

212213
if (!isSubXact)
213-
myproc->xid=xid;
214+
mypgxact->xid=xid;
214215
else
215216
{
216-
intnxids=myproc->subxids.nxids;
217+
intnxids=mypgxact->nxids;
217218

218219
if (nxids<PGPROC_MAX_CACHED_SUBXIDS)
219220
{
220221
myproc->subxids.xids[nxids]=xid;
221-
myproc->subxids.nxids=nxids+1;
222+
mypgxact->nxids=nxids+1;
222223
}
223224
else
224-
myproc->subxids.overflowed= true;
225+
mypgxact->overflowed= true;
225226
}
226227
}
227228

‎src/backend/access/transam/xact.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -981,7 +981,7 @@ RecordTransactionCommit(void)
981981
* bit fuzzy, but it doesn't matter.
982982
*/
983983
START_CRIT_SECTION();
984-
MyProc->inCommit= true;
984+
MyPgXact->inCommit= true;
985985

986986
SetCurrentTransactionStopTimestamp();
987987

@@ -1155,7 +1155,7 @@ RecordTransactionCommit(void)
11551155
*/
11561156
if (markXidCommitted)
11571157
{
1158-
MyProc->inCommit= false;
1158+
MyPgXact->inCommit= false;
11591159
END_CRIT_SECTION();
11601160
}
11611161

‎src/backend/commands/analyze.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -223,7 +223,7 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt, BufferAccessStrategy bstrategy)
223223
* OK, let's do it. First let other backends know I'm in ANALYZE.
224224
*/
225225
LWLockAcquire(ProcArrayLock,LW_EXCLUSIVE);
226-
MyProc->vacuumFlags |=PROC_IN_ANALYZE;
226+
MyPgXact->vacuumFlags |=PROC_IN_ANALYZE;
227227
LWLockRelease(ProcArrayLock);
228228

229229
/*
@@ -250,7 +250,7 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt, BufferAccessStrategy bstrategy)
250250
* because the vacuum flag is cleared by the end-of-xact code.
251251
*/
252252
LWLockAcquire(ProcArrayLock,LW_EXCLUSIVE);
253-
MyProc->vacuumFlags &= ~PROC_IN_ANALYZE;
253+
MyPgXact->vacuumFlags &= ~PROC_IN_ANALYZE;
254254
LWLockRelease(ProcArrayLock);
255255
}
256256

‎src/backend/commands/vacuum.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -893,9 +893,9 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound)
893893
* which is probably Not Good.
894894
*/
895895
LWLockAcquire(ProcArrayLock,LW_EXCLUSIVE);
896-
MyProc->vacuumFlags |=PROC_IN_VACUUM;
896+
MyPgXact->vacuumFlags |=PROC_IN_VACUUM;
897897
if (for_wraparound)
898-
MyProc->vacuumFlags |=PROC_VACUUM_FOR_WRAPAROUND;
898+
MyPgXact->vacuumFlags |=PROC_VACUUM_FOR_WRAPAROUND;
899899
LWLockRelease(ProcArrayLock);
900900
}
901901

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