From ed0b409d22346b1b027a4c2099ca66984d94b6dd Mon Sep 17 00:00:00 2001
From: Robert Haas
Date: Fri, 25 Nov 2011 08:02:10 -0500
Subject: 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
---
 src/backend/storage/lmgr/deadlock.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'src/backend/storage/lmgr/deadlock.c')

diff --git a/src/backend/storage/lmgr/deadlock.c b/src/backend/storage/lmgr/deadlock.c
index 7e7f6af21b7..63326b8770d 100644
--- a/src/backend/storage/lmgr/deadlock.c
+++ b/src/backend/storage/lmgr/deadlock.c
@@ -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 */
-- 
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