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Move "hot" members of PGPROC into a separate PGXACT array.

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This speeds up snapshot-taking and reduces ProcArrayLock contention.
Also, the PGPROC (and PGXACT) structures used by two-phase commit are
now allocated as part of the main array, rather than in a separate
array, and we keep ProcArray sorted in pointer order.  These changes
are intended to minimize the number of cache lines that must be pulled
in to take a snapshot, and testing shows a substantial increase in
performance on both read and write workloads at high concurrencies.

Pavan Deolasee, Heikki Linnakangas, Robert Haas
This commit is contained in:
Robert Haas 2011-11-25 08:02:10 -05:00
parent 9ed439a9c0
commit ed0b409d22
14 changed files with 356 additions and 208 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

115
src/backend/access/transam/twophase.c
View File

@ -113,7 +113,8 @@ int max_prepared_xacts = 0;
typedef struct GlobalTransactionData
{
PGPROC proc; /* dummy proc */
GlobalTransaction next;
int pgprocno; /* dummy proc */
BackendId dummyBackendId; /* similar to backend id for backends */
TimestampTz prepared_at; /* time of preparation */
XLogRecPtr prepare_lsn; /* XLOG offset of prepare record */
@ -207,7 +208,8 @@ TwoPhaseShmemInit(void)
sizeof(GlobalTransaction) * max_prepared_xacts));
for (i = 0; i < max_prepared_xacts; i++)
{
gxacts[i].proc.links.next = (SHM_QUEUE *) TwoPhaseState->freeGXacts;
gxacts[i].pgprocno = PreparedXactProcs[i].pgprocno;
gxacts[i].next = TwoPhaseState->freeGXacts;
TwoPhaseState->freeGXacts = &gxacts[i];
/*
@ -243,6 +245,8 @@ MarkAsPreparing(TransactionId xid, const char *gid,
TimestampTz prepared_at, Oid owner, Oid databaseid)
{
GlobalTransaction gxact;
PGPROC *proc;
PGXACT *pgxact;
int i;
if (strlen(gid) >= GIDSIZE)
@ -274,7 +278,7 @@ MarkAsPreparing(TransactionId xid, const char *gid,
TwoPhaseState->numPrepXacts--;
TwoPhaseState->prepXacts[i] = TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts];
/* and put it back in the freelist */
gxact->proc.links.next = (SHM_QUEUE *) TwoPhaseState->freeGXacts;
gxact->next = TwoPhaseState->freeGXacts;
TwoPhaseState->freeGXacts = gxact;
/* Back up index count too, so we don't miss scanning one */
i--;
@ -302,32 +306,36 @@ MarkAsPreparing(TransactionId xid, const char *gid,
errhint("Increase max_prepared_transactions (currently %d).",
max_prepared_xacts)));
gxact = TwoPhaseState->freeGXacts;
TwoPhaseState->freeGXacts = (GlobalTransaction) gxact->proc.links.next;
TwoPhaseState->freeGXacts = (GlobalTransaction) gxact->next;
/* Initialize it */
MemSet(&gxact->proc, 0, sizeof(PGPROC));
SHMQueueElemInit(&(gxact->proc.links));
gxact->proc.waitStatus = STATUS_OK;
proc = &ProcGlobal->allProcs[gxact->pgprocno];
pgxact = &ProcGlobal->allPgXact[gxact->pgprocno];
/* Initialize the PGPROC entry */
MemSet(proc, 0, sizeof(PGPROC));
proc->pgprocno = gxact->pgprocno;
SHMQueueElemInit(&(proc->links));
proc->waitStatus = STATUS_OK;
/* We set up the gxact's VXID as InvalidBackendId/XID */
gxact->proc.lxid = (LocalTransactionId) xid;
gxact->proc.xid = xid;
gxact->proc.xmin = InvalidTransactionId;
gxact->proc.pid = 0;
gxact->proc.backendId = InvalidBackendId;
gxact->proc.databaseId = databaseid;
gxact->proc.roleId = owner;
gxact->proc.inCommit = false;
gxact->proc.vacuumFlags = 0;
gxact->proc.lwWaiting = false;
gxact->proc.lwExclusive = false;
gxact->proc.lwWaitLink = NULL;
gxact->proc.waitLock = NULL;
gxact->proc.waitProcLock = NULL;
proc->lxid = (LocalTransactionId) xid;
pgxact->xid = xid;
pgxact->xmin = InvalidTransactionId;
pgxact->inCommit = false;
pgxact->vacuumFlags = 0;
proc->pid = 0;
proc->backendId = InvalidBackendId;
proc->databaseId = databaseid;
proc->roleId = owner;
proc->lwWaiting = false;
proc->lwExclusive = false;
proc->lwWaitLink = NULL;
proc->waitLock = NULL;
proc->waitProcLock = NULL;
for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
SHMQueueInit(&(gxact->proc.myProcLocks[i]));
SHMQueueInit(&(proc->myProcLocks[i]));
/* subxid data must be filled later by GXactLoadSubxactData */
gxact->proc.subxids.overflowed = false;
gxact->proc.subxids.nxids = 0;
pgxact->overflowed = false;
pgxact->nxids = 0;
gxact->prepared_at = prepared_at;
/* initialize LSN to 0 (start of WAL) */
@ -358,17 +366,19 @@ static void
GXactLoadSubxactData(GlobalTransaction gxact, int nsubxacts,
TransactionId *children)
{
PGPROC *proc = &ProcGlobal->allProcs[gxact->pgprocno];
PGXACT *pgxact = &ProcGlobal->allPgXact[gxact->pgprocno];
/* We need no extra lock since the GXACT isn't valid yet */
if (nsubxacts > PGPROC_MAX_CACHED_SUBXIDS)
{
gxact->proc.subxids.overflowed = true;
pgxact->overflowed = true;
nsubxacts = PGPROC_MAX_CACHED_SUBXIDS;
}
if (nsubxacts > 0)
{
memcpy(gxact->proc.subxids.xids, children,
memcpy(proc->subxids.xids, children,
nsubxacts * sizeof(TransactionId));
gxact->proc.subxids.nxids = nsubxacts;
pgxact->nxids = nsubxacts;
}
}
@ -389,7 +399,7 @@ MarkAsPrepared(GlobalTransaction gxact)
* Put it into the global ProcArray so TransactionIdIsInProgress considers
* the XID as still running.
*/
ProcArrayAdd(&gxact->proc);
ProcArrayAdd(&ProcGlobal->allProcs[gxact->pgprocno]);
}
/*
@ -406,6 +416,7 @@ LockGXact(const char *gid, Oid user)
for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
{
GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
PGPROC *proc = &ProcGlobal->allProcs[gxact->pgprocno];
/* Ignore not-yet-valid GIDs */
if (!gxact->valid)
@ -436,7 +447,7 @@ LockGXact(const char *gid, Oid user)
* there may be some other issues as well. Hence disallow until
* someone gets motivated to make it work.
*/
if (MyDatabaseId != gxact->proc.databaseId)
if (MyDatabaseId != proc->databaseId)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("prepared transaction belongs to another database"),
@ -483,7 +494,7 @@ RemoveGXact(GlobalTransaction gxact)
TwoPhaseState->prepXacts[i] = TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts];
/* and put it back in the freelist */
gxact->proc.links.next = (SHM_QUEUE *) TwoPhaseState->freeGXacts;
gxact->next = TwoPhaseState->freeGXacts;
TwoPhaseState->freeGXacts = gxact;
LWLockRelease(TwoPhaseStateLock);
@ -518,8 +529,9 @@ TransactionIdIsPrepared(TransactionId xid)
for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
{
GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
PGXACT *pgxact = &ProcGlobal->allPgXact[gxact->pgprocno];
if (gxact->valid && gxact->proc.xid == xid)
if (gxact->valid && pgxact->xid == xid)
{
result = true;
break;
@ -642,6 +654,8 @@ pg_prepared_xact(PG_FUNCTION_ARGS)
while (status->array != NULL && status->currIdx < status->ngxacts)
{
GlobalTransaction gxact = &status->array[status->currIdx++];
PGPROC *proc = &ProcGlobal->allProcs[gxact->pgprocno];
PGXACT *pgxact = &ProcGlobal->allPgXact[gxact->pgprocno];
Datum values[5];
bool nulls[5];
HeapTuple tuple;
@ -656,11 +670,11 @@ pg_prepared_xact(PG_FUNCTION_ARGS)
MemSet(values, 0, sizeof(values));
MemSet(nulls, 0, sizeof(nulls));
values[0] = TransactionIdGetDatum(gxact->proc.xid);
values[0] = TransactionIdGetDatum(pgxact->xid);
values[1] = CStringGetTextDatum(gxact->gid);
values[2] = TimestampTzGetDatum(gxact->prepared_at);
values[3] = ObjectIdGetDatum(gxact->owner);
values[4] = ObjectIdGetDatum(gxact->proc.databaseId);
values[4] = ObjectIdGetDatum(proc->databaseId);
tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
result = HeapTupleGetDatum(tuple);
@ -711,10 +725,11 @@ TwoPhaseGetDummyProc(TransactionId xid)
for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
{
GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
PGXACT *pgxact = &ProcGlobal->allPgXact[gxact->pgprocno];
if (gxact->proc.xid == xid)
if (pgxact->xid == xid)
{
result = &gxact->proc;
result = &ProcGlobal->allProcs[gxact->pgprocno];
break;
}
}
@ -841,7 +856,9 @@ save_state_data(const void *data, uint32 len)
void
StartPrepare(GlobalTransaction gxact)
{
TransactionId xid = gxact->proc.xid;
PGPROC *proc = &ProcGlobal->allProcs[gxact->pgprocno];
PGXACT *pgxact = &ProcGlobal->allPgXact[gxact->pgprocno];
TransactionId xid = pgxact->xid;
TwoPhaseFileHeader hdr;
TransactionId *children;
RelFileNode *commitrels;
@ -865,7 +882,7 @@ StartPrepare(GlobalTransaction gxact)
hdr.magic = TWOPHASE_MAGIC;
hdr.total_len = 0; /* EndPrepare will fill this in */
hdr.xid = xid;
hdr.database = gxact->proc.databaseId;
hdr.database = proc->databaseId;
hdr.prepared_at = gxact->prepared_at;
hdr.owner = gxact->owner;
hdr.nsubxacts = xactGetCommittedChildren(&children);
@ -913,7 +930,8 @@ StartPrepare(GlobalTransaction gxact)
void
EndPrepare(GlobalTransaction gxact)
{
TransactionId xid = gxact->proc.xid;
PGXACT *pgxact = &ProcGlobal->allPgXact[gxact->pgprocno];
TransactionId xid = pgxact->xid;
TwoPhaseFileHeader *hdr;
char path[MAXPGPATH];
XLogRecData *record;
@ -1021,7 +1039,7 @@ EndPrepare(GlobalTransaction gxact)
*/
START_CRIT_SECTION();
MyProc->inCommit = true;
MyPgXact->inCommit = true;
gxact->prepare_lsn = XLogInsert(RM_XACT_ID, XLOG_XACT_PREPARE,
records.head);
@ -1069,7 +1087,7 @@ EndPrepare(GlobalTransaction gxact)
* checkpoint starting after this will certainly see the gxact as a
* candidate for fsyncing.
*/
MyProc->inCommit = false;
MyPgXact->inCommit = false;
END_CRIT_SECTION();
@ -1242,6 +1260,8 @@ void
FinishPreparedTransaction(const char *gid, bool isCommit)
{
GlobalTransaction gxact;
PGPROC *proc;
PGXACT *pgxact;
TransactionId xid;
char *buf;
char *bufptr;
@ -1260,7 +1280,9 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
* try to commit the same GID at once.
*/
gxact = LockGXact(gid, GetUserId());
xid = gxact->proc.xid;
proc = &ProcGlobal->allProcs[gxact->pgprocno];
pgxact = &ProcGlobal->allPgXact[gxact->pgprocno];
xid = pgxact->xid;
/*
* Read and validate the state file
@ -1309,7 +1331,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
hdr->nsubxacts, children,
hdr->nabortrels, abortrels);
ProcArrayRemove(&gxact->proc, latestXid);
ProcArrayRemove(proc, latestXid);
/*
* In case we fail while running the callbacks, mark the gxact invalid so
@ -1540,10 +1562,11 @@ CheckPointTwoPhase(XLogRecPtr redo_horizon)
for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
{
GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
PGXACT *pgxact = &ProcGlobal->allPgXact[gxact->pgprocno];
if (gxact->valid &&
XLByteLE(gxact->prepare_lsn, redo_horizon))
xids[nxids++] = gxact->proc.xid;
xids[nxids++] = pgxact->xid;
}
LWLockRelease(TwoPhaseStateLock);
@ -1972,7 +1995,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
START_CRIT_SECTION();
/* See notes in RecordTransactionCommit */
MyProc->inCommit = true;
MyPgXact->inCommit = true;
/* Emit the XLOG commit record */
xlrec.xid = xid;
@ -2037,7 +2060,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
TransactionIdCommitTree(xid, nchildren, children);
/* Checkpoint can proceed now */
MyProc->inCommit = false;
MyPgXact->inCommit = false;
END_CRIT_SECTION();

11
src/backend/access/transam/varsup.c
View File

@ -54,7 +54,7 @@ GetNewTransactionId(bool isSubXact)
if (IsBootstrapProcessingMode())
{
Assert(!isSubXact);
MyProc->xid = BootstrapTransactionId;
MyPgXact->xid = BootstrapTransactionId;
return BootstrapTransactionId;
}
@ -208,20 +208,21 @@ GetNewTransactionId(bool isSubXact)
* TransactionId and int fetch/store are atomic.
*/
volatile PGPROC *myproc = MyProc;
volatile PGXACT *mypgxact = MyPgXact;
if (!isSubXact)
myproc->xid = xid;
mypgxact->xid = xid;
else
{
int nxids = myproc->subxids.nxids;
int nxids = mypgxact->nxids;
if (nxids < PGPROC_MAX_CACHED_SUBXIDS)
{
myproc->subxids.xids[nxids] = xid;
myproc->subxids.nxids = nxids + 1;
mypgxact->nxids = nxids + 1;
}
else
myproc->subxids.overflowed = true;
mypgxact->overflowed = true;
}
}

4
src/backend/access/transam/xact.c
View File

@ -981,7 +981,7 @@ RecordTransactionCommit(void)
* bit fuzzy, but it doesn't matter.
*/
START_CRIT_SECTION();
MyProc->inCommit = true;
MyPgXact->inCommit = true;
SetCurrentTransactionStopTimestamp();
@ -1155,7 +1155,7 @@ RecordTransactionCommit(void)
*/
if (markXidCommitted)
{
MyProc->inCommit = false;
MyPgXact->inCommit = false;
END_CRIT_SECTION();
}

4
src/backend/commands/analyze.c
View File

@ -223,7 +223,7 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt, BufferAccessStrategy bstrategy)
* OK, let's do it. First let other backends know I'm in ANALYZE.
*/
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
MyProc->vacuumFlags |= PROC_IN_ANALYZE;
MyPgXact->vacuumFlags |= PROC_IN_ANALYZE;
LWLockRelease(ProcArrayLock);
/*
@ -250,7 +250,7 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt, BufferAccessStrategy bstrategy)
* because the vacuum flag is cleared by the end-of-xact code.
*/
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
MyProc->vacuumFlags &= ~PROC_IN_ANALYZE;
MyPgXact->vacuumFlags &= ~PROC_IN_ANALYZE;
LWLockRelease(ProcArrayLock);
}

4
src/backend/commands/vacuum.c
View File

@ -893,9 +893,9 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound)
* which is probably Not Good.
*/
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
MyProc->vacuumFlags |= PROC_IN_VACUUM;
MyPgXact->vacuumFlags |= PROC_IN_VACUUM;
if (for_wraparound)
MyProc->vacuumFlags |= PROC_VACUUM_FOR_WRAPAROUND;
MyPgXact->vacuumFlags |= PROC_VACUUM_FOR_WRAPAROUND;
LWLockRelease(ProcArrayLock);
}

3
src/backend/postmaster/postmaster.c
View File

@ -430,6 +430,7 @@ typedef struct
slock_t *ProcStructLock;
PROC_HDR *ProcGlobal;
PGPROC *AuxiliaryProcs;
PGPROC *PreparedXactProcs;
PMSignalData *PMSignalState;
InheritableSocket pgStatSock;
pid_t PostmasterPid;
@ -4724,6 +4725,7 @@ save_backend_variables(BackendParameters *param, Port *port,
param->ProcStructLock = ProcStructLock;
param->ProcGlobal = ProcGlobal;
param->AuxiliaryProcs = AuxiliaryProcs;
param->PreparedXactProcs = PreparedXactProcs;
param->PMSignalState = PMSignalState;
if (!write_inheritable_socket(&param->pgStatSock, pgStatSock, childPid))
return false;
@ -4947,6 +4949,7 @@ restore_backend_variables(BackendParameters *param, Port *port)
ProcStructLock = param->ProcStructLock;
ProcGlobal = param->ProcGlobal;
AuxiliaryProcs = param->AuxiliaryProcs;
PreparedXactProcs = param->PreparedXactProcs;
PMSignalState = param->PMSignalState;
read_inheritable_socket(&pgStatSock, &param->pgStatSock);

2
src/backend/replication/walsender.c
View File

@ -702,7 +702,7 @@ ProcessStandbyHSFeedbackMessage(void)
* safe, and if we're moving it backwards, well, the data is at risk
* already since a VACUUM could have just finished calling GetOldestXmin.)
*/
MyProc->xmin = reply.xmin;
MyPgXact->xmin = reply.xmin;
}
/* Main loop of walsender process */

2
src/backend/storage/ipc/ipci.c
View File

@ -192,7 +192,6 @@ CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
XLOGShmemInit();
CLOGShmemInit();
SUBTRANSShmemInit();
TwoPhaseShmemInit();
MultiXactShmemInit();
InitBufferPool();
@ -213,6 +212,7 @@ CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
InitProcGlobal();
CreateSharedProcArray();
CreateSharedBackendStatus();
TwoPhaseShmemInit();
/*
* Set up shared-inval messaging

276
src/backend/storage/ipc/procarray.c
View File

@ -82,14 +82,17 @@ typedef struct ProcArrayStruct
TransactionId lastOverflowedXid;
/*
* We declare procs[] as 1 entry because C wants a fixed-size array, but
* We declare pgprocnos[] as 1 entry because C wants a fixed-size array, but
* actually it is maxProcs entries long.
*/
PGPROC *procs[1]; /* VARIABLE LENGTH ARRAY */
int pgprocnos[1]; /* VARIABLE LENGTH ARRAY */
} ProcArrayStruct;
static ProcArrayStruct *procArray;
static PGPROC *allProcs;
static PGXACT *allPgXact;
/*
* Bookkeeping for tracking emulated transactions in recovery
*/
@ -169,8 +172,8 @@ ProcArrayShmemSize(void)
/* Size of the ProcArray structure itself */
#define PROCARRAY_MAXPROCS (MaxBackends + max_prepared_xacts)
size = offsetof(ProcArrayStruct, procs);
size = add_size(size, mul_size(sizeof(PGPROC *), PROCARRAY_MAXPROCS));
size = offsetof(ProcArrayStruct, pgprocnos);
size = add_size(size, mul_size(sizeof(int), PROCARRAY_MAXPROCS));
/*
* During Hot Standby processing we have a data structure called
@ -211,8 +214,8 @@ CreateSharedProcArray(void)
/* Create or attach to the ProcArray shared structure */
procArray = (ProcArrayStruct *)
ShmemInitStruct("Proc Array",
add_size(offsetof(ProcArrayStruct, procs),
mul_size(sizeof(PGPROC *),
add_size(offsetof(ProcArrayStruct, pgprocnos),
mul_size(sizeof(int),
PROCARRAY_MAXPROCS)),
&found);
@ -231,6 +234,9 @@ CreateSharedProcArray(void)
procArray->lastOverflowedXid = InvalidTransactionId;
}
allProcs = ProcGlobal->allProcs;
allPgXact = ProcGlobal->allPgXact;
/* Create or attach to the KnownAssignedXids arrays too, if needed */
if (EnableHotStandby)
{
@ -253,6 +259,7 @@ void
ProcArrayAdd(PGPROC *proc)
{
ProcArrayStruct *arrayP = procArray;
int index;
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
@ -269,7 +276,28 @@ ProcArrayAdd(PGPROC *proc)
errmsg("sorry, too many clients already")));
}
arrayP->procs[arrayP->numProcs] = proc;
/*
* Keep the procs array sorted by (PGPROC *) so that we can utilize
* locality of references much better. This is useful while traversing the
* ProcArray because there is a increased likelyhood of finding the next
* PGPROC structure in the cache.
*
* Since the occurance of adding/removing a proc is much lower than the
* access to the ProcArray itself, the overhead should be marginal
*/
for (index = 0; index < arrayP->numProcs; index++)
{
/*
* If we are the first PGPROC or if we have found our right position in
* the array, break
*/
if ((arrayP->pgprocnos[index] == -1) || (arrayP->pgprocnos[index] > proc->pgprocno))
break;
}
memmove(&arrayP->pgprocnos[index + 1], &arrayP->pgprocnos[index],
(arrayP->numProcs - index) * sizeof (int));
arrayP->pgprocnos[index] = proc->pgprocno;
arrayP->numProcs++;
LWLockRelease(ProcArrayLock);
@ -301,7 +329,7 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
if (TransactionIdIsValid(latestXid))
{
Assert(TransactionIdIsValid(proc->xid));
Assert(TransactionIdIsValid(allPgXact[proc->pgprocno].xid));
/* Advance global latestCompletedXid while holding the lock */
if (TransactionIdPrecedes(ShmemVariableCache->latestCompletedXid,
@ -311,15 +339,17 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
else
{
/* Shouldn't be trying to remove a live transaction here */
Assert(!TransactionIdIsValid(proc->xid));
Assert(!TransactionIdIsValid(allPgXact[proc->pgprocno].xid));
}
for (index = 0; index < arrayP->numProcs; index++)
{
if (arrayP->procs[index] == proc)
if (arrayP->pgprocnos[index] == proc->pgprocno)
{
arrayP->procs[index] = arrayP->procs[arrayP->numProcs - 1];
arrayP->procs[arrayP->numProcs - 1] = NULL; /* for debugging */
/* Keep the PGPROC array sorted. See notes above */
memmove(&arrayP->pgprocnos[index], &arrayP->pgprocnos[index + 1],
(arrayP->numProcs - index - 1) * sizeof (int));
arrayP->pgprocnos[arrayP->numProcs - 1] = -1; /* for debugging */
arrayP->numProcs--;
LWLockRelease(ProcArrayLock);
return;
@ -349,29 +379,31 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
void
ProcArrayEndTransaction(PGPROC *proc, TransactionId latestXid)
{
PGXACT *pgxact = &allPgXact[proc->pgprocno];
if (TransactionIdIsValid(latestXid))
{
/*
* We must lock ProcArrayLock while clearing proc->xid, so that we do
* not exit the set of "running" transactions while someone else is
* taking a snapshot. See discussion in
* We must lock ProcArrayLock while clearing our advertised XID, so
* that we do not exit the set of "running" transactions while someone
* else is taking a snapshot. See discussion in
* src/backend/access/transam/README.
*/
Assert(TransactionIdIsValid(proc->xid));
Assert(TransactionIdIsValid(allPgXact[proc->pgprocno].xid));
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
proc->xid = InvalidTransactionId;
pgxact->xid = InvalidTransactionId;
proc->lxid = InvalidLocalTransactionId;
proc->xmin = InvalidTransactionId;
pgxact->xmin = InvalidTransactionId;
/* must be cleared with xid/xmin: */
proc->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
proc->inCommit = false; /* be sure this is cleared in abort */
pgxact->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
pgxact->inCommit = false; /* be sure this is cleared in abort */
proc->recoveryConflictPending = false;
/* Clear the subtransaction-XID cache too while holding the lock */
proc->subxids.nxids = 0;
proc->subxids.overflowed = false;
pgxact->nxids = 0;
pgxact->overflowed = false;
/* Also advance global latestCompletedXid while holding the lock */
if (TransactionIdPrecedes(ShmemVariableCache->latestCompletedXid,
@ -387,17 +419,17 @@ ProcArrayEndTransaction(PGPROC *proc, TransactionId latestXid)
* anyone else's calculation of a snapshot. We might change their
* estimate of global xmin, but that's OK.
*/
Assert(!TransactionIdIsValid(proc->xid));
Assert(!TransactionIdIsValid(allPgXact[proc->pgprocno].xid));
proc->lxid = InvalidLocalTransactionId;
proc->xmin = InvalidTransactionId;
pgxact->xmin = InvalidTransactionId;
/* must be cleared with xid/xmin: */
proc->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
proc->inCommit = false; /* be sure this is cleared in abort */
pgxact->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
pgxact->inCommit = false; /* be sure this is cleared in abort */
proc->recoveryConflictPending = false;
Assert(proc->subxids.nxids == 0);
Assert(proc->subxids.overflowed == false);
Assert(pgxact->nxids == 0);
Assert(pgxact->overflowed == false);
}
}
@ -413,24 +445,26 @@ ProcArrayEndTransaction(PGPROC *proc, TransactionId latestXid)
void
ProcArrayClearTransaction(PGPROC *proc)
{
PGXACT *pgxact = &allPgXact[proc->pgprocno];
/*
* We can skip locking ProcArrayLock here, because this action does not
* actually change anyone's view of the set of running XIDs: our entry is
* duplicate with the gxact that has already been inserted into the
* ProcArray.
*/
proc->xid = InvalidTransactionId;
pgxact->xid = InvalidTransactionId;
proc->lxid = InvalidLocalTransactionId;
proc->xmin = InvalidTransactionId;
pgxact->xmin = InvalidTransactionId;
proc->recoveryConflictPending = false;
/* redundant, but just in case */
proc->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
proc->inCommit = false;
pgxact->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
pgxact->inCommit = false;
/* Clear the subtransaction-XID cache too */
proc->subxids.nxids = 0;
proc->subxids.overflowed = false;
pgxact->nxids = 0;
pgxact->overflowed = false;
}
/*
@ -811,15 +845,17 @@ TransactionIdIsInProgress(TransactionId xid)
/* No shortcuts, gotta grovel through the array */
for (i = 0; i < arrayP->numProcs; i++)
{
volatile PGPROC *proc = arrayP->procs[i];
TransactionId pxid;
int pgprocno = arrayP->pgprocnos[i];
volatile PGPROC *proc = &allProcs[pgprocno];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
TransactionId pxid;
/* Ignore my own proc --- dealt with it above */
if (proc == MyProc)
continue;
/* Fetch xid just once - see GetNewTransactionId */
pxid = proc->xid;
pxid = pgxact->xid;
if (!TransactionIdIsValid(pxid))
continue;
@ -844,7 +880,7 @@ TransactionIdIsInProgress(TransactionId xid)
/*
* Step 2: check the cached child-Xids arrays
*/
for (j = proc->subxids.nxids - 1; j >= 0; j--)
for (j = pgxact->nxids - 1; j >= 0; j--)
{
/* Fetch xid just once - see GetNewTransactionId */
TransactionId cxid = proc->subxids.xids[j];
@ -864,7 +900,7 @@ TransactionIdIsInProgress(TransactionId xid)
* we hold ProcArrayLock. So we can't miss an Xid that we need to
* worry about.)
*/
if (proc->subxids.overflowed)
if (pgxact->overflowed)
xids[nxids++] = pxid;
}
@ -965,10 +1001,13 @@ TransactionIdIsActive(TransactionId xid)
for (i = 0; i < arrayP->numProcs; i++)
{
volatile PGPROC *proc = arrayP->procs[i];
int pgprocno = arrayP->pgprocnos[i];
volatile PGPROC *proc = &allProcs[pgprocno];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
TransactionId pxid;
/* Fetch xid just once - see GetNewTransactionId */
TransactionId pxid = proc->xid;
pxid = pgxact->xid;
if (!TransactionIdIsValid(pxid))
continue;
@ -1060,9 +1099,11 @@ GetOldestXmin(bool allDbs, bool ignoreVacuum)
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGPROC *proc = &allProcs[pgprocno];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
if (ignoreVacuum && (proc->vacuumFlags & PROC_IN_VACUUM))
if (ignoreVacuum && (pgxact->vacuumFlags & PROC_IN_VACUUM))
continue;
if (allDbs ||
@ -1070,7 +1111,7 @@ GetOldestXmin(bool allDbs, bool ignoreVacuum)
proc->databaseId == 0) /* always include WalSender */
{
/* Fetch xid just once - see GetNewTransactionId */
TransactionId xid = proc->xid;
TransactionId xid = pgxact->xid;
/* First consider the transaction's own Xid, if any */
if (TransactionIdIsNormal(xid) &&
@ -1084,7 +1125,7 @@ GetOldestXmin(bool allDbs, bool ignoreVacuum)
* have an Xmin but not (yet) an Xid; conversely, if it has an
* Xid, that could determine some not-yet-set Xmin.
*/
xid = proc->xmin; /* Fetch just once */
xid = pgxact->xmin; /* Fetch just once */
if (TransactionIdIsNormal(xid) &&
TransactionIdPrecedes(xid, result))
result = xid;
@ -1261,31 +1302,33 @@ GetSnapshotData(Snapshot snapshot)
if (!snapshot->takenDuringRecovery)
{
int *pgprocnos = arrayP->pgprocnos;
int numProcs;
/*
* Spin over procArray checking xid, xmin, and subxids. The goal is
* to gather all active xids, find the lowest xmin, and try to record
* subxids. During recovery no xids will be assigned, so all normal
* backends can be ignored, nor are there any VACUUMs running. All
* prepared transaction xids are held in KnownAssignedXids, so these
* will be seen without needing to loop through procs here.
* subxids.
*/
for (index = 0; index < arrayP->numProcs; index++)
numProcs = arrayP->numProcs;
for (index = 0; index < numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
TransactionId xid;
int pgprocno = pgprocnos[index];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
TransactionId xid;
/* Ignore procs running LAZY VACUUM */
if (proc->vacuumFlags & PROC_IN_VACUUM)
if (pgxact->vacuumFlags & PROC_IN_VACUUM)
continue;
/* Update globalxmin to be the smallest valid xmin */
xid = proc->xmin; /* fetch just once */
xid = pgxact->xmin; /* fetch just once */
if (TransactionIdIsNormal(xid) &&
TransactionIdPrecedes(xid, globalxmin))
globalxmin = xid;
globalxmin = xid;
/* Fetch xid just once - see GetNewTransactionId */
xid = proc->xid;
xid = pgxact->xid;
/*
* If the transaction has been assigned an xid < xmax we add it to
@ -1300,7 +1343,7 @@ GetSnapshotData(Snapshot snapshot)
{
if (TransactionIdFollowsOrEquals(xid, xmax))
continue;
if (proc != MyProc)
if (pgxact != MyPgXact)
snapshot->xip[count++] = xid;
if (TransactionIdPrecedes(xid, xmin))
xmin = xid;
@ -1321,16 +1364,17 @@ GetSnapshotData(Snapshot snapshot)
*
* Again, our own XIDs are not included in the snapshot.
*/
if (!suboverflowed && proc != MyProc)
if (!suboverflowed && pgxact != MyPgXact)
{
if (proc->subxids.overflowed)
if (pgxact->overflowed)
suboverflowed = true;
else
{
int nxids = proc->subxids.nxids;
int nxids = pgxact->nxids;
if (nxids > 0)
{
volatile PGPROC *proc = &allProcs[pgprocno];
memcpy(snapshot->subxip + subcount,
(void *) proc->subxids.xids,
nxids * sizeof(TransactionId));
@ -1372,9 +1416,8 @@ GetSnapshotData(Snapshot snapshot)
suboverflowed = true;
}
if (!TransactionIdIsValid(MyProc->xmin))
MyProc->xmin = TransactionXmin = xmin;
if (!TransactionIdIsValid(MyPgXact->xmin))
MyPgXact->xmin = TransactionXmin = xmin;
LWLockRelease(ProcArrayLock);
/*
@ -1436,14 +1479,16 @@ ProcArrayInstallImportedXmin(TransactionId xmin, TransactionId sourcexid)
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
TransactionId xid;
int pgprocno = arrayP->pgprocnos[index];
volatile PGPROC *proc = &allProcs[pgprocno];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
TransactionId xid;
/* Ignore procs running LAZY VACUUM */
if (proc->vacuumFlags & PROC_IN_VACUUM)
if (pgxact->vacuumFlags & PROC_IN_VACUUM)
continue;
xid = proc->xid; /* fetch just once */
xid = pgxact->xid; /* fetch just once */
if (xid != sourcexid)
continue;
@ -1459,7 +1504,7 @@ ProcArrayInstallImportedXmin(TransactionId xmin, TransactionId sourcexid)
/*
* Likewise, let's just make real sure its xmin does cover us.
*/
xid = proc->xmin; /* fetch just once */
xid = pgxact->xmin; /* fetch just once */
if (!TransactionIdIsNormal(xid) ||
!TransactionIdPrecedesOrEquals(xid, xmin))
continue;
@ -1470,7 +1515,7 @@ ProcArrayInstallImportedXmin(TransactionId xmin, TransactionId sourcexid)
* GetSnapshotData first, we'll be overwriting a valid xmin here,
* so we don't check that.)
*/
MyProc->xmin = TransactionXmin = xmin;
MyPgXact->xmin = TransactionXmin = xmin;
result = true;
break;
@ -1562,12 +1607,14 @@ GetRunningTransactionData(void)
*/
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGPROC *proc = &allProcs[pgprocno];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
TransactionId xid;
int nxids;
/* Fetch xid just once - see GetNewTransactionId */
xid = proc->xid;
xid = pgxact->xid;
/*
* We don't need to store transactions that don't have a TransactionId
@ -1585,7 +1632,7 @@ GetRunningTransactionData(void)
* Save subtransaction XIDs. Other backends can't add or remove
* entries while we're holding XidGenLock.
*/
nxids = proc->subxids.nxids;
nxids = pgxact->nxids;
if (nxids > 0)
{
memcpy(&xids[count], (void *) proc->subxids.xids,
@ -1593,7 +1640,7 @@ GetRunningTransactionData(void)
count += nxids;
subcount += nxids;
if (proc->subxids.overflowed)
if (pgxact->overflowed)
suboverflowed = true;
/*
@ -1653,11 +1700,12 @@ GetOldestActiveTransactionId(void)
*/
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
TransactionId xid;
/* Fetch xid just once - see GetNewTransactionId */
xid = proc->xid;
xid = pgxact->xid;
if (!TransactionIdIsNormal(xid))
continue;
@ -1709,12 +1757,14 @@ GetTransactionsInCommit(TransactionId **xids_p)
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
TransactionId pxid;
/* Fetch xid just once - see GetNewTransactionId */
TransactionId pxid = proc->xid;
pxid = pgxact->xid;
if (proc->inCommit && TransactionIdIsValid(pxid))
if (pgxact->inCommit && TransactionIdIsValid(pxid))
xids[nxids++] = pxid;
}
@ -1744,12 +1794,14 @@ HaveTransactionsInCommit(TransactionId *xids, int nxids)
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
TransactionId pxid;
/* Fetch xid just once - see GetNewTransactionId */
TransactionId pxid = proc->xid;
pxid = pgxact->xid;
if (proc->inCommit && TransactionIdIsValid(pxid))
if (pgxact->inCommit && TransactionIdIsValid(pxid))
{
int i;
@ -1792,7 +1844,7 @@ BackendPidGetProc(int pid)
for (index = 0; index < arrayP->numProcs; index++)
{
PGPROC *proc = arrayP->procs[index];
PGPROC *proc = &allProcs[arrayP->pgprocnos[index]];
if (proc->pid == pid)
{
@ -1833,9 +1885,11 @@ BackendXidGetPid(TransactionId xid)
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGPROC *proc = &allProcs[pgprocno];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
if (proc->xid == xid)
if (pgxact->xid == xid)
{
result = proc->pid;
break;
@ -1901,18 +1955,20 @@ GetCurrentVirtualXIDs(TransactionId limitXmin, bool excludeXmin0,
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGPROC *proc = &allProcs[pgprocno];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
if (proc == MyProc)
continue;
if (excludeVacuum & proc->vacuumFlags)
if (excludeVacuum & pgxact->vacuumFlags)
continue;
if (allDbs || proc->databaseId == MyDatabaseId)
{
/* Fetch xmin just once - might change on us */
TransactionId pxmin = proc->xmin;
TransactionId pxmin = pgxact->xmin;
if (excludeXmin0 && !TransactionIdIsValid(pxmin))
continue;
@ -1996,7 +2052,9 @@ GetConflictingVirtualXIDs(TransactionId limitXmin, Oid dbOid)
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGPROC *proc = &allProcs[pgprocno];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
/* Exclude prepared transactions */
if (proc->pid == 0)
@ -2006,7 +2064,7 @@ GetConflictingVirtualXIDs(TransactionId limitXmin, Oid dbOid)
proc->databaseId == dbOid)
{
/* Fetch xmin just once - can't change on us, but good coding */
TransactionId pxmin = proc->xmin;
TransactionId pxmin = pgxact->xmin;
/*
* We ignore an invalid pxmin because this means that backend has
@ -2050,8 +2108,9 @@ CancelVirtualTransaction(VirtualTransactionId vxid, ProcSignalReason sigmode)
for (index = 0; index < arrayP->numProcs; index++)
{
VirtualTransactionId procvxid;
PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGPROC *proc = &allProcs[pgprocno];
VirtualTransactionId procvxid;
GET_VXID_FROM_PGPROC(procvxid, *proc);
@ -2104,7 +2163,9 @@ MinimumActiveBackends(int min)
*/
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGPROC *proc = &allProcs[pgprocno];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
/*
* Since we're not holding a lock, need to check that the pointer is
@ -2122,10 +2183,10 @@ MinimumActiveBackends(int min)
if (proc == MyProc)
continue; /* do not count myself */
if (pgxact->xid == InvalidTransactionId)
continue; /* do not count if no XID assigned */
if (proc->pid == 0)
continue; /* do not count prepared xacts */
if (proc->xid == InvalidTransactionId)
continue; /* do not count if no XID assigned */
if (proc->waitLock != NULL)
continue; /* do not count if blocked on a lock */
count++;
@ -2150,7 +2211,8 @@ CountDBBackends(Oid databaseid)
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGPROC *proc = &allProcs[pgprocno];
if (proc->pid == 0)
continue; /* do not count prepared xacts */
@ -2179,7 +2241,8 @@ CancelDBBackends(Oid databaseid, ProcSignalReason sigmode, bool conflictPending)
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGPROC *proc = &allProcs[pgprocno];
if (databaseid == InvalidOid || proc->databaseId == databaseid)
{
@ -2217,7 +2280,8 @@ CountUserBackends(Oid roleid)
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGPROC *proc = &allProcs[pgprocno];
if (proc->pid == 0)
continue; /* do not count prepared xacts */
@ -2277,7 +2341,9 @@ CountOtherDBBackends(Oid databaseId, int *nbackends, int *nprepared)
for (index = 0; index < arrayP->numProcs; index++)
{
volatile PGPROC *proc = arrayP->procs[index];
int pgprocno = arrayP->pgprocnos[index];
volatile PGPROC *proc = &allProcs[pgprocno];
volatile PGXACT *pgxact = &allPgXact[pgprocno];
if (proc->databaseId != databaseId)
continue;
@ -2291,7 +2357,7 @@ CountOtherDBBackends(Oid databaseId, int *nbackends, int *nprepared)
else
{
(*nbackends)++;
if ((proc->vacuumFlags & PROC_IS_AUTOVACUUM) &&
if ((pgxact->vacuumFlags & PROC_IS_AUTOVACUUM) &&
nautovacs < MAXAUTOVACPIDS)
autovac_pids[nautovacs++] = proc->pid;
}
@ -2321,8 +2387,8 @@ CountOtherDBBackends(Oid databaseId, int *nbackends, int *nprepared)
#define XidCacheRemove(i) \
do { \
MyProc->subxids.xids[i] = MyProc->subxids.xids[MyProc->subxids.nxids - 1]; \
MyProc->subxids.nxids--; \
MyProc->subxids.xids[i] = MyProc->subxids.xids[MyPgXact->nxids - 1]; \
MyPgXact->nxids--; \
} while (0)
/*
@ -2361,7 +2427,7 @@ XidCacheRemoveRunningXids(TransactionId xid,
{
TransactionId anxid = xids[i];
for (j = MyProc->subxids.nxids - 1; j >= 0; j--)
for (j = MyPgXact->nxids - 1; j >= 0; j--)
{
if (TransactionIdEquals(MyProc->subxids.xids[j], anxid))
{
@ -2377,11 +2443,11 @@ XidCacheRemoveRunningXids(TransactionId xid,
* error during AbortSubTransaction. So instead of Assert, emit a
* debug warning.
*/
if (j < 0 && !MyProc->subxids.overflowed)
if (j < 0 && !MyPgXact->overflowed)
elog(WARNING, "did not find subXID %u in MyProc", anxid);
}
for (j = MyProc->subxids.nxids - 1; j >= 0; j--)
for (j = MyPgXact->nxids - 1; j >= 0; j--)
{
if (TransactionIdEquals(MyProc->subxids.xids[j], xid))
{
@ -2390,7 +2456,7 @@ XidCacheRemoveRunningXids(TransactionId xid,
}
}
/* Ordinarily we should have found it, unless the cache has overflowed */
if (j < 0 && !MyProc->subxids.overflowed)
if (j < 0 && !MyPgXact->overflowed)
elog(WARNING, "did not find subXID %u in MyProc", xid);
/* Also advance global latestCompletedXid while holding the lock */

4
src/backend/storage/lmgr/deadlock.c
View File

@ -450,6 +450,7 @@ FindLockCycleRecurse(PGPROC *checkProc,
int *nSoftEdges) /* output argument */
{
PGPROC *proc;
PGXACT *pgxact;
LOCK *lock;
PROCLOCK *proclock;
SHM_QUEUE *procLocks;
@ -516,6 +517,7 @@ FindLockCycleRecurse(PGPROC *checkProc,
while (proclock)
{
proc = proclock->tag.myProc;
pgxact = &ProcGlobal->allPgXact[proc->pgprocno];
/* A proc never blocks itself */
if (proc != checkProc)
@ -541,7 +543,7 @@ FindLockCycleRecurse(PGPROC *checkProc,
* vacuumFlag bit), but we don't do that here to avoid
* grabbing ProcArrayLock.
*/
if (proc->vacuumFlags & PROC_IS_AUTOVACUUM)
if (pgxact->vacuumFlags & PROC_IS_AUTOVACUUM)
blocking_autovacuum_proc = proc;
/* This proc hard-blocks checkProc */

3
src/backend/storage/lmgr/lock.c
View File

@ -3188,9 +3188,10 @@ GetRunningTransactionLocks(int *nlocks)
proclock->tag.myLock->tag.locktag_type == LOCKTAG_RELATION)
{
PGPROC *proc = proclock->tag.myProc;
PGXACT *pgxact = &ProcGlobal->allPgXact[proc->pgprocno];
LOCK *lock = proclock->tag.myLock;
accessExclusiveLocks[index].xid = proc->xid;
accessExclusiveLocks[index].xid = pgxact->xid;
accessExclusiveLocks[index].dbOid = lock->tag.locktag_field1;
accessExclusiveLocks[index].relOid = lock->tag.locktag_field2;

87
src/backend/storage/lmgr/proc.c
View File

@ -36,6 +36,7 @@
#include <sys/time.h>
#include "access/transam.h"
#include "access/twophase.h"
#include "access/xact.h"
#include "miscadmin.h"
#include "postmaster/autovacuum.h"
@ -57,6 +58,7 @@ bool log_lock_waits = false;
/* Pointer to this process's PGPROC struct, if any */
PGPROC *MyProc = NULL;
PGXACT *MyPgXact = NULL;
/*
* This spinlock protects the freelist of recycled PGPROC structures.
@ -70,6 +72,7 @@ NON_EXEC_STATIC slock_t *ProcStructLock = NULL;
/* Pointers to shared-memory structures */
PROC_HDR *ProcGlobal = NULL;
NON_EXEC_STATIC PGPROC *AuxiliaryProcs = NULL;
PGPROC *PreparedXactProcs = NULL;
/* If we are waiting for a lock, this points to the associated LOCALLOCK */
static LOCALLOCK *lockAwaited = NULL;
@ -106,13 +109,19 @@ ProcGlobalShmemSize(void)
/* ProcGlobal */
size = add_size(size, sizeof(PROC_HDR));
/* AuxiliaryProcs */
size = add_size(size, mul_size(NUM_AUXILIARY_PROCS, sizeof(PGPROC)));
/* MyProcs, including autovacuum workers and launcher */
size = add_size(size, mul_size(MaxBackends, sizeof(PGPROC)));
/* AuxiliaryProcs */
size = add_size(size, mul_size(NUM_AUXILIARY_PROCS, sizeof(PGPROC)));
/* Prepared xacts */
size = add_size(size, mul_size(max_prepared_xacts, sizeof(PGPROC)));
/* ProcStructLock */
size = add_size(size, sizeof(slock_t));
size = add_size(size, mul_size(MaxBackends, sizeof(PGXACT)));
size = add_size(size, mul_size(NUM_AUXILIARY_PROCS, sizeof(PGXACT)));
size = add_size(size, mul_size(max_prepared_xacts, sizeof(PGXACT)));
return size;
}
@ -157,10 +166,11 @@ void
InitProcGlobal(void)
{
PGPROC *procs;
PGXACT *pgxacts;
int i,
j;
bool found;
uint32 TotalProcs = MaxBackends + NUM_AUXILIARY_PROCS;
uint32 TotalProcs = MaxBackends + NUM_AUXILIARY_PROCS + max_prepared_xacts;
/* Create the ProcGlobal shared structure */
ProcGlobal = (PROC_HDR *)
@ -182,10 +192,11 @@ InitProcGlobal(void)
* those used for 2PC, which are embedded within a GlobalTransactionData
* struct).
*
* There are three separate consumers of PGPROC structures: (1) normal
* backends, (2) autovacuum workers and the autovacuum launcher, and (3)
* auxiliary processes. Each PGPROC structure is dedicated to exactly
* one of these purposes, and they do not move between groups.
* There are four separate consumers of PGPROC structures: (1) normal
* backends, (2) autovacuum workers and the autovacuum launcher, (3)
* auxiliary processes, and (4) prepared transactions. Each PGPROC
* structure is dedicated to exactly one of these purposes, and they do
* not move between groups.
*/
procs = (PGPROC *) ShmemAlloc(TotalProcs * sizeof(PGPROC));
ProcGlobal->allProcs = procs;
@ -195,21 +206,43 @@ InitProcGlobal(void)
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of shared memory")));
MemSet(procs, 0, TotalProcs * sizeof(PGPROC));
/*
* Also allocate a separate array of PGXACT structures. This is separate
* from the main PGPROC array so that the most heavily accessed data is
* stored contiguously in memory in as few cache lines as possible. This
* provides significant performance benefits, especially on a
* multiprocessor system. Thereis one PGXACT structure for every PGPROC
* structure.
*/
pgxacts = (PGXACT *) ShmemAlloc(TotalProcs * sizeof(PGXACT));
MemSet(pgxacts, 0, TotalProcs * sizeof(PGXACT));
ProcGlobal->allPgXact = pgxacts;
for (i = 0; i < TotalProcs; i++)
{
/* Common initialization for all PGPROCs, regardless of type. */
/* Set up per-PGPROC semaphore, latch, and backendLock */
PGSemaphoreCreate(&(procs[i].sem));
InitSharedLatch(&(procs[i].procLatch));
procs[i].backendLock = LWLockAssign();
/*
* Set up per-PGPROC semaphore, latch, and backendLock. Prepared
* xact dummy PGPROCs don't need these though - they're never
* associated with a real process
*/
if (i < MaxBackends + NUM_AUXILIARY_PROCS)
{
PGSemaphoreCreate(&(procs[i].sem));
InitSharedLatch(&(procs[i].procLatch));
procs[i].backendLock = LWLockAssign();
}
procs[i].pgprocno = i;
/*
* Newly created PGPROCs for normal backends or for autovacuum must
* be queued up on the appropriate free list. Because there can only
* ever be a small, fixed number of auxiliary processes, no free
* list is used in that case; InitAuxiliaryProcess() instead uses a
* linear search.
* linear search. PGPROCs for prepared transactions are added to a
* free list by TwoPhaseShmemInit().
*/
if (i < MaxConnections)
{
@ -230,10 +263,11 @@ InitProcGlobal(void)
}
/*
* Save a pointer to the block of PGPROC structures reserved for
* auxiliary proceses.
* Save pointers to the blocks of PGPROC structures reserved for
* auxiliary processes and prepared transactions.
*/
AuxiliaryProcs = &procs[MaxBackends];
PreparedXactProcs = &procs[MaxBackends + NUM_AUXILIARY_PROCS];
/* Create ProcStructLock spinlock, too */
ProcStructLock = (slock_t *) ShmemAlloc(sizeof(slock_t));
@ -296,6 +330,7 @@ InitProcess(void)
(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
errmsg("sorry, too many clients already")));
}
MyPgXact = &ProcGlobal->allPgXact[MyProc->pgprocno];
/*
* Now that we have a PGPROC, mark ourselves as an active postmaster
@ -313,18 +348,18 @@ InitProcess(void)
SHMQueueElemInit(&(MyProc->links));
MyProc->waitStatus = STATUS_OK;
MyProc->lxid = InvalidLocalTransactionId;
MyProc->xid = InvalidTransactionId;
MyProc->xmin = InvalidTransactionId;
MyPgXact->xid = InvalidTransactionId;
MyPgXact->xmin = InvalidTransactionId;
MyProc->pid = MyProcPid;
/* backendId, databaseId and roleId will be filled in later */
MyProc->backendId = InvalidBackendId;
MyProc->databaseId = InvalidOid;
MyProc->roleId = InvalidOid;
MyProc->inCommit = false;
MyProc->vacuumFlags = 0;
MyPgXact->inCommit = false;
MyPgXact->vacuumFlags = 0;
/* NB -- autovac launcher intentionally does not set IS_AUTOVACUUM */
if (IsAutoVacuumWorkerProcess())
MyProc->vacuumFlags |= PROC_IS_AUTOVACUUM;
MyPgXact->vacuumFlags |= PROC_IS_AUTOVACUUM;
MyProc->lwWaiting = false;
MyProc->lwExclusive = false;
MyProc->lwWaitLink = NULL;
@ -462,6 +497,7 @@ InitAuxiliaryProcess(void)
((volatile PGPROC *) auxproc)->pid = MyProcPid;
MyProc = auxproc;
MyPgXact = &ProcGlobal->allPgXact[auxproc->pgprocno];
SpinLockRelease(ProcStructLock);
@ -472,13 +508,13 @@ InitAuxiliaryProcess(void)
SHMQueueElemInit(&(MyProc->links));
MyProc->waitStatus = STATUS_OK;
MyProc->lxid = InvalidLocalTransactionId;
MyProc->xid = InvalidTransactionId;
MyProc->xmin = InvalidTransactionId;
MyPgXact->xid = InvalidTransactionId;
MyPgXact->xmin = InvalidTransactionId;
MyProc->backendId = InvalidBackendId;
MyProc->databaseId = InvalidOid;
MyProc->roleId = InvalidOid;
MyProc->inCommit = false;
MyProc->vacuumFlags = 0;
MyPgXact->inCommit = false;
MyPgXact->vacuumFlags = 0;
MyProc->lwWaiting = false;
MyProc->lwExclusive = false;
MyProc->lwWaitLink = NULL;
@ -1045,6 +1081,7 @@ ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
if (deadlock_state == DS_BLOCKED_BY_AUTOVACUUM && allow_autovacuum_cancel)
{
PGPROC *autovac = GetBlockingAutoVacuumPgproc();
PGXACT *autovac_pgxact = &ProcGlobal->allPgXact[autovac->pgprocno];
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
@ -1053,8 +1090,8 @@ ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
* wraparound.
*/
if ((autovac != NULL) &&
(autovac->vacuumFlags & PROC_IS_AUTOVACUUM) &&
!(autovac->vacuumFlags & PROC_VACUUM_FOR_WRAPAROUND))
(autovac_pgxact->vacuumFlags & PROC_IS_AUTOVACUUM) &&
!(autovac_pgxact->vacuumFlags & PROC_VACUUM_FOR_WRAPAROUND))
{
int pid = autovac->pid;

2
src/backend/utils/time/snapmgr.c
View File

@ -577,7 +577,7 @@ static void
SnapshotResetXmin(void)
{
if (RegisteredSnapshots == 0 && ActiveSnapshot == NULL)
MyProc->xmin = InvalidTransactionId;
MyPgXact->xmin = InvalidTransactionId;
}
/*

47
src/include/storage/proc.h
View File

@ -35,8 +35,6 @@
struct XidCache
{
bool overflowed;
int nxids;
TransactionId xids[PGPROC_MAX_CACHED_SUBXIDS];
};
@ -86,27 +84,14 @@ struct PGPROC
LocalTransactionId lxid; /* local id of top-level transaction currently
* being executed by this proc, if running;
* else InvalidLocalTransactionId */
TransactionId xid; /* id of top-level transaction currently being
* executed by this proc, if running and XID
* is assigned; else InvalidTransactionId */
TransactionId xmin; /* minimal running XID as it was when we were
* starting our xact, excluding LAZY VACUUM:
* vacuum must not remove tuples deleted by
* xid >= xmin ! */
int pid; /* Backend's process ID; 0 if prepared xact */
int pgprocno;
/* These fields are zero while a backend is still starting up: */
BackendId backendId; /* This backend's backend ID (if assigned) */
Oid databaseId; /* OID of database this backend is using */
Oid roleId; /* OID of role using this backend */
bool inCommit; /* true if within commit critical section */
uint8 vacuumFlags; /* vacuum-related flags, see above */
/*
* While in hot standby mode, shows that a conflict signal has been sent
* for the current transaction. Set/cleared while holding ProcArrayLock,
@ -160,7 +145,33 @@ struct PGPROC
extern PGDLLIMPORT PGPROC *MyProc;
extern PGDLLIMPORT struct PGXACT *MyPgXact;
/*
* Prior to PostgreSQL 9.2, the fieds below were stored as part of the
* PGPROC. However, benchmarking revealed that packing these particular
* members into a separate array as tightly as possible sped up GetSnapshotData
* considerably on systems with many CPU cores, by reducing the number of
* cache lines needing to be fetched. Thus, think very carefully before adding
* anything else here.
*/
typedef struct PGXACT
{
TransactionId xid; /* id of top-level transaction currently being
* executed by this proc, if running and XID
* is assigned; else InvalidTransactionId */
TransactionId xmin; /* minimal running XID as it was when we were
* starting our xact, excluding LAZY VACUUM:
* vacuum must not remove tuples deleted by
* xid >= xmin ! */
uint8 vacuumFlags; /* vacuum-related flags, see above */
bool overflowed;
bool inCommit; /* true if within commit critical section */
uint8 nxids;
} PGXACT;
/*
* There is one ProcGlobal struct for the whole database cluster.
@ -169,6 +180,8 @@ typedef struct PROC_HDR
{
/* Array of PGPROC structures (not including dummies for prepared txns) */
PGPROC *allProcs;
/* Array of PGXACT structures (not including dummies for prepared txns */
PGXACT *allPgXact;
/* Length of allProcs array */
uint32 allProcCount;
/* Head of list of free PGPROC structures */
@ -186,6 +199,8 @@ typedef struct PROC_HDR
extern PROC_HDR *ProcGlobal;
extern PGPROC *PreparedXactProcs;
/*
* We set aside some extra PGPROC structures for auxiliary processes,
* ie things that aren't full-fledged backends but need shmem access.