From 455db18cb525d151f0dee40738023efbcdecdae4 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Tue, 10 Feb 2026 22:47:22 +0200 Subject: [PATCH v2 4/4] Rearrange fields in PGPROC, for clarity --- src/include/storage/proc.h | 124 +++++++++++++++++++++---------------- 1 file changed, 71 insertions(+), 53 deletions(-) diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h index f642830fcf8..b1077562cb5 100644 --- a/src/include/storage/proc.h +++ b/src/include/storage/proc.h @@ -184,27 +184,31 @@ typedef struct PGPROC dlist_node freeProcsLink; /* link in procgloballist, when in recycled * state */ - PGSemaphore sem; /* ONE semaphore to sleep on */ - ProcWaitStatus waitStatus; - - Latch procLatch; /* generic latch for process */ + /*---- Backend identity ----*/ + /* + * These fields that don't change after backend startup, or only very + * rarely + */ + int pid; /* Backend's process ID; 0 if prepared xact */ + BackendType backendType; /* what kind of process is this? */ - TransactionId xid; /* id of top-level transaction currently being - * executed by this proc, if running and XID - * is assigned; else InvalidTransactionId. - * mirrored in ProcGlobal->xids[pgxactoff] */ - - 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 ! */ + /* These fields are zero while a backend is still starting up: */ + Oid databaseId; /* OID of database this backend is using */ + Oid roleId; /* OID of role using this backend */ - int pid; /* Backend's process ID; 0 if prepared xact */ + 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] */ + + /*---- Transactions and snapshots ----*/ + /* * Currently running top-level transaction's virtual xid. Together these * form a VirtualTransactionId, but we don't use that struct because this @@ -224,14 +228,27 @@ typedef struct PGPROC * InvalidLocalTransactionId */ } vxid; - /* These fields are zero while a backend is still starting up: */ - Oid databaseId; /* OID of database this backend is using */ - Oid roleId; /* OID of role using this backend */ + TransactionId xid; /* id of top-level transaction currently being + * executed by this proc, if running and XID + * is assigned; else InvalidTransactionId. + * mirrored in ProcGlobal->xids[pgxactoff] */ - Oid tempNamespaceId; /* OID of temp schema this backend is - * using */ + 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 ! */ - BackendType backendType; /* what kind of process is this? */ + XidCacheStatus subxidStatus; /* mirrored with + * ProcGlobal->subxidStates[i] */ + struct XidCache subxids; /* cache for subtransaction XIDs */ + + /*---- Inter-process signaling ----*/ + + Latch procLatch; /* generic latch for process */ + + PGSemaphore sem; /* ONE semaphore to sleep on */ + + int delayChkptFlags; /* for DELAY_CHKPT_* flags */ /* * While in hot standby mode, shows that a conflict signal has been sent @@ -243,6 +260,8 @@ typedef struct PGPROC */ pg_atomic_uint32 pendingRecoveryConflicts; + /*---- LWLock waiting ----*/ + /* * Info about LWLock the process is currently waiting for, if any. * @@ -257,6 +276,16 @@ typedef struct PGPROC /* Support for condition variables. */ proclist_node cvWaitLink; /* position in CV wait list */ + /*---- Lock manager data ----*/ + + /* + * Support for lock groups. Use LockHashPartitionLockByProc on the group + * leader to get the LWLock protecting these fields. + */ + PGPROC *lockGroupLeader; /* lock group leader, if I'm a member */ + dlist_head lockGroupMembers; /* list of members, if I'm a leader */ + dlist_node lockGroupLink; /* my member link, if I'm a member */ + /* Info about lock the process is currently waiting for, if any. */ /* waitLock and waitProcLock are NULL if not currently waiting. */ LOCK *waitLock; /* Lock object we're sleeping on ... */ @@ -265,14 +294,28 @@ typedef struct PGPROC LOCKMODE waitLockMode; /* type of lock we're waiting for */ LOCKMASK heldLocks; /* bitmask for lock types already held on this * lock object by this backend */ + pg_atomic_uint64 waitStart; /* time at which wait for lock acquisition * started */ - int delayChkptFlags; /* for DELAY_CHKPT_* flags */ + ProcWaitStatus waitStatus; - uint8 statusFlags; /* this backend's status flags, see PROC_* - * above. mirrored in - * ProcGlobal->statusFlags[pgxactoff] */ + /* + * All PROCLOCK objects for locks held or awaited by this backend are + * linked into one of these lists, according to the partition number of + * their lock. + */ + dlist_head myProcLocks[NUM_LOCK_PARTITIONS]; + + /*-- recording fast-path locks taken by this backend. --*/ + LWLock fpInfoLock; /* protects per-backend fast-path state */ + uint64 *fpLockBits; /* lock modes held for each fast-path slot */ + Oid *fpRelId; /* slots for rel oids */ + bool fpVXIDLock; /* are we holding a fast-path VXID lock? */ + LocalTransactionId fpLocalTransactionId; /* lxid for fast-path VXID + * lock */ + + /*---- Synchronous replication waiting ----*/ /* * Info to allow us to wait for synchronous replication, if needed. @@ -284,18 +327,8 @@ typedef struct PGPROC int syncRepState; /* wait state for sync rep */ dlist_node syncRepLinks; /* list link if process is in syncrep queue */ - /* - * All PROCLOCK objects for locks held or awaited by this backend are - * linked into one of these lists, according to the partition number of - * their lock. - */ - dlist_head myProcLocks[NUM_LOCK_PARTITIONS]; - - XidCacheStatus subxidStatus; /* mirrored with - * ProcGlobal->subxidStates[i] */ - struct XidCache subxids; /* cache for subtransaction XIDs */ + /*---- Support for group XID clearing. ----*/ - /* Support for group XID clearing. */ /* true, if member of ProcArray group waiting for XID clear */ bool procArrayGroupMember; /* next ProcArray group member waiting for XID clear */ @@ -307,9 +340,7 @@ typedef struct PGPROC */ TransactionId procArrayGroupMemberXid; - uint32 wait_event_info; /* proc's wait information */ - - /* Support for group transaction status update. */ + /*---- Support for group transaction status update. ----*/ bool clogGroupMember; /* true, if member of clog group */ pg_atomic_uint32 clogGroupNext; /* next clog group member */ TransactionId clogGroupMemberXid; /* transaction id of clog group member */ @@ -320,21 +351,8 @@ typedef struct PGPROC XLogRecPtr clogGroupMemberLsn; /* WAL location of commit record for clog * group member */ - /* Lock manager data, recording fast-path locks taken by this backend. */ - LWLock fpInfoLock; /* protects per-backend fast-path state */ - uint64 *fpLockBits; /* lock modes held for each fast-path slot */ - Oid *fpRelId; /* slots for rel oids */ - bool fpVXIDLock; /* are we holding a fast-path VXID lock? */ - LocalTransactionId fpLocalTransactionId; /* lxid for fast-path VXID - * lock */ - - /* - * Support for lock groups. Use LockHashPartitionLockByProc on the group - * leader to get the LWLock protecting these fields. - */ - PGPROC *lockGroupLeader; /* lock group leader, if I'm a member */ - dlist_head lockGroupMembers; /* list of members, if I'm a leader */ - dlist_node lockGroupLink; /* my member link, if I'm a member */ + /*---- Status reporting ----*/ + uint32 wait_event_info; /* proc's wait information */ } /* -- 2.47.3