From cc75db39184b6560ded5f97b5202c14187e9f801 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Fri, 20 Feb 2026 22:30:01 +0200 Subject: [PATCH v2 1/2] Rearrange fields in PGPROC, for clarity The ordering was pretty random, making it hard to get an overview of what's in it. Group related fields together, and add comments to act as separators between the groups. Reviewed-by: Bertrand Drouvot Discussion: https://www.postgresql.org/message-id/3dd6f70c-b94d-4428-8e75-74a7136396be@iki.fi --- src/include/storage/proc.h | 147 +++++++++++++++++++++++-------------- 1 file changed, 92 insertions(+), 55 deletions(-) diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h index e165b414241..b2fd4d02959 100644 --- a/src/include/storage/proc.h +++ b/src/include/storage/proc.h @@ -178,33 +178,41 @@ typedef enum * * See PROC_HDR for details. */ -struct PGPROC +typedef struct PGPROC { dlist_head *procgloballist; /* procglobal list that owns this 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 +232,30 @@ 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 +267,10 @@ struct PGPROC */ pg_atomic_uint32 pendingRecoveryConflicts; + /************************************************************************ + * LWLock waiting + ************************************************************************/ + /* * Info about LWLock the process is currently waiting for, if any. * @@ -257,6 +285,18 @@ 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 +305,30 @@ 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 +340,10 @@ 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 +355,10 @@ 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 */ @@ -320,24 +369,12 @@ 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 */ + /************************************************************************ + * Status reporting + ************************************************************************/ - /* - * 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 */ -}; - -/* NOTE: "typedef struct PGPROC PGPROC" appears in storage/lock.h. */ + uint32 wait_event_info; /* proc's wait information */ +} PGPROC; extern PGDLLIMPORT PGPROC *MyProc; -- 2.47.3