From 2b28c29d68eb2c37137aef66c7634b65aa640520 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Wed, 13 Oct 2021 10:31:26 +0900
Subject: [PATCH v2 1/5] procfreelist in ascending order

---
 src/backend/storage/lmgr/proc.c | 62 +++++++++++++++++++--------------
 1 file changed, 36 insertions(+), 26 deletions(-)

diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index b7d9da0aa9..78e05976a4 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -163,6 +163,9 @@ InitProcGlobal(void)
 				j;
 	bool		found;
 	uint32		TotalProcs = MaxBackends + NUM_AUXILIARY_PROCS + max_prepared_xacts;
+	PGPROC	  **freelist;
+	int			switchpoint;
+	int			arraykind;
 
 	/* Create the ProcGlobal shared structure */
 	ProcGlobal = (PROC_HDR *)
@@ -214,6 +217,8 @@ InitProcGlobal(void)
 	ProcGlobal->statusFlags = (uint8 *) ShmemAlloc(TotalProcs * sizeof(*ProcGlobal->statusFlags));
 	MemSet(ProcGlobal->statusFlags, 0, TotalProcs * sizeof(*ProcGlobal->statusFlags));
 
+	switchpoint = 0;
+	arraykind = 0;
 	for (i = 0; i < TotalProcs; i++)
 	{
 		/* Common initialization for all PGPROCs, regardless of type. */
@@ -239,33 +244,38 @@ InitProcGlobal(void)
 		 * linear search.   PGPROCs for prepared transactions are added to a
 		 * free list by TwoPhaseShmemInit().
 		 */
-		if (i < MaxConnections)
+		if (i < MaxBackends)
 		{
-			/* PGPROC for normal backend, add to freeProcs list */
-			procs[i].links.next = (SHM_QUEUE *) ProcGlobal->freeProcs;
-			ProcGlobal->freeProcs = &procs[i];
-			procs[i].procgloballist = &ProcGlobal->freeProcs;
-		}
-		else if (i < MaxConnections + autovacuum_max_workers + 1)
-		{
-			/* PGPROC for AV launcher/worker, add to autovacFreeProcs list */
-			procs[i].links.next = (SHM_QUEUE *) ProcGlobal->autovacFreeProcs;
-			ProcGlobal->autovacFreeProcs = &procs[i];
-			procs[i].procgloballist = &ProcGlobal->autovacFreeProcs;
-		}
-		else if (i < MaxConnections + autovacuum_max_workers + 1 + max_worker_processes)
-		{
-			/* PGPROC for bgworker, add to bgworkerFreeProcs list */
-			procs[i].links.next = (SHM_QUEUE *) ProcGlobal->bgworkerFreeProcs;
-			ProcGlobal->bgworkerFreeProcs = &procs[i];
-			procs[i].procgloballist = &ProcGlobal->bgworkerFreeProcs;
-		}
-		else if (i < MaxBackends)
-		{
-			/* PGPROC for walsender, add to walsenderFreeProcs list */
-			procs[i].links.next = (SHM_QUEUE *) ProcGlobal->walsenderFreeProcs;
-			ProcGlobal->walsenderFreeProcs = &procs[i];
-			procs[i].procgloballist = &ProcGlobal->walsenderFreeProcs;
+			if (i == switchpoint)
+			{
+				switch (arraykind++)
+				{
+					case 0:
+						freelist = &ProcGlobal->freeProcs;
+						switchpoint += MaxConnections;
+						break;
+
+					case 1:
+						freelist = &ProcGlobal->autovacFreeProcs;
+						switchpoint += autovacuum_max_workers + 1;
+						break;
+
+					case 2:
+						freelist = &ProcGlobal->bgworkerFreeProcs;
+						switchpoint += max_worker_processes;
+						break;
+
+					case 3:
+						freelist = &ProcGlobal->walsenderFreeProcs;
+				}
+
+				/* link the element to the just-switched freelist */
+				*freelist = &procs[i];
+			}
+			else
+				procs[i - 1].links.next = (SHM_QUEUE *) &procs[i];
+
+			procs[i].procgloballist = freelist;
 		}
 
 		/* Initialize myProcLocks[] shared memory queues. */
-- 
2.27.0