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

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

1 files changed, 3 insertions, 0 deletions

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 6758083bdd5..963189d4150 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -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);