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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
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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;