From 5e8b84fcfe4ecccc1847ed8d70d428e1fc5bc59f Mon Sep 17 00:00:00 2001 From: Maksim Melnikov Date: Tue, 18 Nov 2025 17:20:09 +0300 Subject: [PATCH v2] This patch reduce connection init/close time. ProcArrayRemove/ProcArrayAdd are expensive in terms of accessing pgxactoff field in PGPROC, because its are placed on different pages and it the reason of page_faults occurence. Now one of the use case with pgxactoff is iteration with gaps over PGPROCs and read/write pgxactoff, PGPROC allocate ~1KB and it quite enough to have page_faults in case of such accessing. So we placed all pgxactoff in the separate array pgxactoffs to have adjacent pages for them all. Indexes in allProcs aligned with pgxactoffs array, so the Nth element in pgxactoffs refer to Nth PGPROC. Eventually it helps to avoid extra page_faults and reduce connection init/close time. --- src/backend/access/transam/varsup.c | 10 +++--- src/backend/commands/indexcmds.c | 2 +- src/backend/commands/vacuum.c | 2 +- src/backend/replication/logical/logical.c | 2 +- src/backend/replication/slot.c | 2 +- src/backend/replication/walsender.c | 2 +- src/backend/storage/ipc/procarray.c | 40 +++++++++++++---------- src/backend/storage/lmgr/proc.c | 6 +++- src/include/storage/proc.h | 6 ++-- 9 files changed, 40 insertions(+), 32 deletions(-) diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c index dc5e32d86f3..1bbc1bcd665 100644 --- a/src/backend/access/transam/varsup.c +++ b/src/backend/access/transam/varsup.c @@ -85,7 +85,7 @@ GetNewTransactionId(bool isSubXact) { Assert(!isSubXact); MyProc->xid = BootstrapTransactionId; - ProcGlobal->xids[MyProc->pgxactoff] = BootstrapTransactionId; + ProcGlobal->xids[ProcGetMyXactOff()] = BootstrapTransactionId; return FullTransactionIdFromEpochAndXid(0, BootstrapTransactionId); } @@ -244,18 +244,18 @@ GetNewTransactionId(bool isSubXact) */ if (!isSubXact) { - Assert(ProcGlobal->subxidStates[MyProc->pgxactoff].count == 0); - Assert(!ProcGlobal->subxidStates[MyProc->pgxactoff].overflowed); + Assert(ProcGlobal->subxidStates[ProcGetMyXactOff()].count == 0); + Assert(!ProcGlobal->subxidStates[ProcGetMyXactOff()].overflowed); Assert(MyProc->subxidStatus.count == 0); Assert(!MyProc->subxidStatus.overflowed); /* LWLockRelease acts as barrier */ MyProc->xid = xid; - ProcGlobal->xids[MyProc->pgxactoff] = xid; + ProcGlobal->xids[ProcGetMyXactOff()] = xid; } else { - XidCacheStatus *substat = &ProcGlobal->subxidStates[MyProc->pgxactoff]; + XidCacheStatus *substat = &ProcGlobal->subxidStates[ProcGetMyXactOff()]; int nxids = MyProc->subxidStatus.count; Assert(substat->count == MyProc->subxidStatus.count); diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c index 9ab74c8df0a..d9e83e26c78 100644 --- a/src/backend/commands/indexcmds.c +++ b/src/backend/commands/indexcmds.c @@ -4654,6 +4654,6 @@ set_indexsafe_procflags(void) LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); MyProc->statusFlags |= PROC_IN_SAFE_IC; - ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags; + ProcGlobal->statusFlags[ProcGetMyXactOff()] = MyProc->statusFlags; LWLockRelease(ProcArrayLock); } diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c index a4abb29cf64..884d18fad4e 100644 --- a/src/backend/commands/vacuum.c +++ b/src/backend/commands/vacuum.c @@ -2059,7 +2059,7 @@ vacuum_rel(Oid relid, RangeVar *relation, VacuumParams params, MyProc->statusFlags |= PROC_IN_VACUUM; if (params.is_wraparound) MyProc->statusFlags |= PROC_VACUUM_FOR_WRAPAROUND; - ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags; + ProcGlobal->statusFlags[ProcGetMyXactOff()] = MyProc->statusFlags; LWLockRelease(ProcArrayLock); } diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index 3541fc793e4..c2c96a70c92 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -188,7 +188,7 @@ StartupDecodingContext(List *output_plugin_options, { LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); MyProc->statusFlags |= PROC_IN_LOGICAL_DECODING; - ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags; + ProcGlobal->statusFlags[ProcGetMyXactOff()] = MyProc->statusFlags; LWLockRelease(ProcArrayLock); } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index d7fb9f5a67f..1bd3b8f902b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -832,7 +832,7 @@ ReplicationSlotRelease(void) /* might not have been set when we've been a plain slot */ LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); MyProc->statusFlags &= ~PROC_IN_LOGICAL_DECODING; - ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags; + ProcGlobal->statusFlags[ProcGetMyXactOff()] = MyProc->statusFlags; LWLockRelease(ProcArrayLock); if (am_walsender) diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c index 04aa770d981..748b47a15bf 100644 --- a/src/backend/replication/walsender.c +++ b/src/backend/replication/walsender.c @@ -358,7 +358,7 @@ InitWalSender(void) Assert(MyProc->xmin == InvalidTransactionId); LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); MyProc->statusFlags |= PROC_AFFECTS_ALL_HORIZONS; - ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags; + ProcGlobal->statusFlags[ProcGetMyXactOff()] = MyProc->statusFlags; LWLockRelease(ProcArrayLock); } diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..585ed6d3677 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -283,6 +283,7 @@ typedef enum KAXCompressReason } KAXCompressReason; static PGPROC *allProcs; +static int *pgxactoffs; /* * Cache to reduce overhead of repeated calls to TransactionIdIsInProgress() @@ -449,6 +450,7 @@ ProcArrayShmemInit(void *arg) TransamVariables->xactCompletionCount = 1; allProcs = ProcGlobal->allProcs; + pgxactoffs = ProcGlobal->pgxactoffs; } static void @@ -498,7 +500,7 @@ ProcArrayAdd(PGPROC *proc) int this_procno = arrayP->pgprocnos[index]; Assert(this_procno >= 0 && this_procno < (arrayP->maxProcs + NUM_AUXILIARY_PROCS)); - Assert(allProcs[this_procno].pgxactoff == index); + Assert(pgxactoffs[this_procno] == index); /* If we have found our right position in the array, break */ if (this_procno > pgprocno) @@ -520,7 +522,7 @@ ProcArrayAdd(PGPROC *proc) movecount * sizeof(*ProcGlobal->statusFlags)); arrayP->pgprocnos[index] = GetNumberFromPGProc(proc); - proc->pgxactoff = index; + pgxactoffs[arrayP->pgprocnos[index]] = index; ProcGlobal->xids[index] = proc->xid; ProcGlobal->subxidStates[index] = proc->subxidStatus; ProcGlobal->statusFlags[index] = proc->statusFlags; @@ -534,9 +536,9 @@ ProcArrayAdd(PGPROC *proc) int procno = arrayP->pgprocnos[index]; Assert(procno >= 0 && procno < (arrayP->maxProcs + NUM_AUXILIARY_PROCS)); - Assert(allProcs[procno].pgxactoff == index - 1); + Assert(pgxactoffs[procno] == index - 1); - allProcs[procno].pgxactoff = index; + pgxactoffs[procno] = index; } /* @@ -574,10 +576,10 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid) LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); LWLockAcquire(XidGenLock, LW_EXCLUSIVE); - myoff = proc->pgxactoff; + myoff = ProcGetXactOff(GetNumberFromPGProc(proc)); Assert(myoff >= 0 && myoff < arrayP->numProcs); - Assert(ProcGlobal->allProcs[arrayP->pgprocnos[myoff]].pgxactoff == myoff); + Assert(ProcGlobal->pgxactoffs[arrayP->pgprocnos[myoff]] == myoff); if (TransactionIdIsValid(latestXid)) { @@ -632,9 +634,9 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid) int procno = arrayP->pgprocnos[index]; Assert(procno >= 0 && procno < (arrayP->maxProcs + NUM_AUXILIARY_PROCS)); - Assert(allProcs[procno].pgxactoff - 1 == index); + Assert(pgxactoffs[procno] - 1 == index); - allProcs[procno].pgxactoff = index; + pgxactoffs[procno] = index; } /* @@ -706,11 +708,13 @@ ProcArrayEndTransaction(PGPROC *proc, TransactionId latestXid) /* avoid unnecessarily dirtying shared cachelines */ if (proc->statusFlags & PROC_VACUUM_STATE_MASK) { + int pgxactoff = ProcGetXactOff(GetNumberFromPGProc(proc)); + Assert(!LWLockHeldByMe(ProcArrayLock)); LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); - Assert(proc->statusFlags == ProcGlobal->statusFlags[proc->pgxactoff]); + Assert(proc->statusFlags == ProcGlobal->statusFlags[pgxactoff]); proc->statusFlags &= ~PROC_VACUUM_STATE_MASK; - ProcGlobal->statusFlags[proc->pgxactoff] = proc->statusFlags; + ProcGlobal->statusFlags[pgxactoff] = proc->statusFlags; LWLockRelease(ProcArrayLock); } } @@ -724,7 +728,7 @@ ProcArrayEndTransaction(PGPROC *proc, TransactionId latestXid) static inline void ProcArrayEndTransactionInternal(PGPROC *proc, TransactionId latestXid) { - int pgxactoff = proc->pgxactoff; + int pgxactoff = ProcGetXactOff(GetNumberFromPGProc(proc)); /* * Note: we need exclusive lock here because we're going to change other @@ -747,7 +751,7 @@ ProcArrayEndTransactionInternal(PGPROC *proc, TransactionId latestXid) if (proc->statusFlags & PROC_VACUUM_STATE_MASK) { proc->statusFlags &= ~PROC_VACUUM_STATE_MASK; - ProcGlobal->statusFlags[proc->pgxactoff] = proc->statusFlags; + ProcGlobal->statusFlags[pgxactoff] = proc->statusFlags; } /* Clear the subtransaction-XID cache too while holding the lock */ @@ -916,7 +920,7 @@ ProcArrayClearTransaction(PGPROC *proc) */ LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); - pgxactoff = proc->pgxactoff; + pgxactoff = ProcGetXactOff(GetNumberFromPGProc(proc)); ProcGlobal->xids[pgxactoff] = InvalidTransactionId; proc->xid = InvalidTransactionId; @@ -1475,7 +1479,7 @@ TransactionIdIsInProgress(TransactionId xid) } /* No shortcuts, gotta grovel through the array */ - mypgxactoff = MyProc->pgxactoff; + mypgxactoff = ProcGetMyXactOff(); numProcs = arrayP->numProcs; for (int pgxactoff = 0; pgxactoff < numProcs; pgxactoff++) { @@ -2176,7 +2180,7 @@ GetSnapshotData(Snapshot snapshot) } latest_completed = TransamVariables->latestCompletedXid; - mypgxactoff = MyProc->pgxactoff; + mypgxactoff = ProcGetMyXactOff(); myxid = other_xids[mypgxactoff]; Assert(myxid == MyProc->xid); @@ -2215,7 +2219,7 @@ GetSnapshotData(Snapshot snapshot) TransactionId xid = UINT32_ACCESS_ONCE(other_xids[pgxactoff]); uint8 statusFlags; - Assert(allProcs[arrayP->pgprocnos[pgxactoff]].pgxactoff == pgxactoff); + Assert(pgxactoffs[arrayP->pgprocnos[pgxactoff]] == pgxactoff); /* * If the transaction has no XID assigned, we can skip it; it @@ -2583,7 +2587,7 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) MyProc->xmin = TransactionXmin = xmin; MyProc->statusFlags = (MyProc->statusFlags & ~PROC_XMIN_FLAGS) | (proc->statusFlags & PROC_XMIN_FLAGS); - ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags; + ProcGlobal->statusFlags[ProcGetMyXactOff()] = MyProc->statusFlags; result = true; } @@ -4011,7 +4015,7 @@ XidCacheRemoveRunningXids(TransactionId xid, */ LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); - mysubxidstat = &ProcGlobal->subxidStates[MyProc->pgxactoff]; + mysubxidstat = &ProcGlobal->subxidStates[ProcGetMyXactOff()]; /* * Under normal circumstances xid and xids[] will be in increasing order, diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c index 6fa9de33e1c..1a52bdb8b88 100644 --- a/src/backend/storage/lmgr/proc.c +++ b/src/backend/storage/lmgr/proc.c @@ -164,6 +164,7 @@ ProcGlobalShmemRequest(void *arg) size = add_size(size, mul_size(TotalProcs, sizeof(PGPROC))); size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->xids))); size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->subxidStates))); + size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->pgxactoffs))); size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->statusFlags))); ProcGlobalAllProcsShmemSize = size; ShmemRequestStruct(.name = "PGPROC structures", @@ -270,6 +271,9 @@ ProcGlobalShmemInit(void *arg) ProcGlobal->subxidStates = (XidCacheStatus *) ptr; ptr = ptr + (TotalProcs * sizeof(*ProcGlobal->subxidStates)); + ProcGlobal->pgxactoffs = (int *) ptr; + ptr = (char *) ptr + TotalProcs * sizeof(*ProcGlobal->pgxactoffs); + ProcGlobal->statusFlags = (uint8 *) ptr; ptr = ptr + (TotalProcs * sizeof(*ProcGlobal->statusFlags)); @@ -1531,7 +1535,7 @@ ProcSleep(LOCALLOCK *locallock) * the lock held, which is much more undesirable. */ LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); - statusFlags = ProcGlobal->statusFlags[autovac->pgxactoff]; + statusFlags = ProcGlobal->statusFlags[ProcGetXactOff(GetNumberFromPGProc(autovac))]; lockmethod_copy = lock->tag.locktag_lockmethodid; locktag_copy = lock->tag; LWLockRelease(ProcArrayLock); diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h index 3e1d1fad5f9..2c4d23cb116 100644 --- a/src/include/storage/proc.h +++ b/src/include/storage/proc.h @@ -210,9 +210,6 @@ typedef struct PGPROC Oid tempNamespaceId; /* OID of temp schema this backend is * using */ - int pgxactoff; /* offset into various ProcGlobal->arrays with - * data mirrored from this PGPROC */ - uint8 statusFlags; /* this backend's status flags, see PROC_* * above. mirrored in * ProcGlobal->statusFlags[pgxactoff] */ @@ -445,6 +442,7 @@ typedef struct PROC_HDR { /* Array of PGPROC structures (not including dummies for prepared txns) */ PGPROC *allProcs; + int *pgxactoffs; /* Array mirroring PGPROC.xid for each PGPROC currently in the procarray */ TransactionId *xids; @@ -509,6 +507,8 @@ extern PGDLLIMPORT PGPROC *PreparedXactProcs; */ #define GetPGProcByNumber(n) (&ProcGlobal->allProcs[(n)]) #define GetNumberFromPGProc(proc) ((proc) - &ProcGlobal->allProcs[0]) +#define ProcGetXactOff(procno) (ProcGlobal->pgxactoffs[(procno)]) +#define ProcGetMyXactOff() (ProcGetXactOff(GetNumberFromPGProc(MyProc))) /* * We set aside some extra PGPROC structures for "special worker" processes, -- 2.43.0