v2-0001-Optimize-ProcSendSignal.patch

From 5c2d78110d5efb61f40cf741948a4b247c0bddaf Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Thu, 11 Mar 2021 23:09:11 +1300
Subject: [PATCH v2] Optimize ProcSendSignal().

Instead of referring to target processes by pid, use pgprocno so that we
don't have to scan the ProcArray and keep track of the startup process.

Discussion: https://postgr.es/m/CA%2BhUKGLYRyDaneEwz5Uya_OgFLMx5BgJfkQSD%3Dq9HmwsfRRb-w%40mail.gmail.com
---
 src/backend/access/transam/xlog.c         |  1 -
 src/backend/storage/buffer/buf_init.c     |  3 +-
 src/backend/storage/buffer/bufmgr.c       | 10 ++---
 src/backend/storage/lmgr/predicate.c      |  5 ++-
 src/backend/storage/lmgr/proc.c           | 49 ++---------------------
 src/include/storage/buf_internals.h       |  2 +-
 src/include/storage/predicate_internals.h |  1 +
 src/include/storage/proc.h                |  6 +--
 8 files changed, 17 insertions(+), 60 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 441a9124cd..6a394f3583 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -7281,7 +7281,6 @@ StartupXLOG(void)
 		 */
 		if (ArchiveRecoveryRequested && IsUnderPostmaster)
 		{
-			PublishStartupProcessInformation();
 			EnableSyncRequestForwarding();
 			SendPostmasterSignal(PMSIGNAL_RECOVERY_STARTED);
 			bgwriterLaunched = true;
diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c
index a299be1043..b9a83c0e9b 100644
--- a/src/backend/storage/buffer/buf_init.c
+++ b/src/backend/storage/buffer/buf_init.c
@@ -16,6 +16,7 @@
 
 #include "storage/buf_internals.h"
 #include "storage/bufmgr.h"
+#include "storage/proc.h"
 
 BufferDescPadded *BufferDescriptors;
 char	   *BufferBlocks;
@@ -118,7 +119,7 @@ InitBufferPool(void)
 			CLEAR_BUFFERTAG(buf->tag);
 
 			pg_atomic_init_u32(&buf->state, 0);
-			buf->wait_backend_pid = 0;
+			buf->wait_backend_pgprocno = INVALID_PGPROCNO;
 
 			buf->buf_id = i;
 
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 4b296a22c4..ab3506f05b 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -1896,11 +1896,11 @@ UnpinBuffer(BufferDesc *buf, bool fixOwner)
 				BUF_STATE_GET_REFCOUNT(buf_state) == 1)
 			{
 				/* we just released the last pin other than the waiter's */
-				int			wait_backend_pid = buf->wait_backend_pid;
+				int			wait_backend_pgprocno = buf->wait_backend_pgprocno;
 
 				buf_state &= ~BM_PIN_COUNT_WAITER;
 				UnlockBufHdr(buf, buf_state);
-				ProcSendSignal(wait_backend_pid);
+				ProcSendSignal(wait_backend_pgprocno);
 			}
 			else
 				UnlockBufHdr(buf, buf_state);
@@ -4007,7 +4007,7 @@ UnlockBuffers(void)
 		 * got a cancel/die interrupt before getting the signal.
 		 */
 		if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
-			buf->wait_backend_pid == MyProcPid)
+			buf->wait_backend_pgprocno == MyProc->pgprocno)
 			buf_state &= ~BM_PIN_COUNT_WAITER;
 
 		UnlockBufHdr(buf, buf_state);
@@ -4143,7 +4143,7 @@ LockBufferForCleanup(Buffer buffer)
 			LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
 			elog(ERROR, "multiple backends attempting to wait for pincount 1");
 		}
-		bufHdr->wait_backend_pid = MyProcPid;
+		bufHdr->wait_backend_pgprocno = MyProc->pgprocno;
 		PinCountWaitBuf = bufHdr;
 		buf_state |= BM_PIN_COUNT_WAITER;
 		UnlockBufHdr(bufHdr, buf_state);
@@ -4214,7 +4214,7 @@ LockBufferForCleanup(Buffer buffer)
 		 */
 		buf_state = LockBufHdr(bufHdr);
 		if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
-			bufHdr->wait_backend_pid == MyProcPid)
+			bufHdr->wait_backend_pgprocno == MyProc->pgprocno)
 			buf_state &= ~BM_PIN_COUNT_WAITER;
 		UnlockBufHdr(bufHdr, buf_state);
 
diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c
index d493aeef0f..c151e0c30c 100644
--- a/src/backend/storage/lmgr/predicate.c
+++ b/src/backend/storage/lmgr/predicate.c
@@ -1876,6 +1876,7 @@ GetSerializableTransactionSnapshotInt(Snapshot snapshot,
 	sxact->finishedBefore = InvalidTransactionId;
 	sxact->xmin = snapshot->xmin;
 	sxact->pid = MyProcPid;
+	sxact->pgprocno = MyProc->pgprocno;
 	SHMQueueInit(&(sxact->predicateLocks));
 	SHMQueueElemInit(&(sxact->finishedLink));
 	sxact->flags = 0;
@@ -3669,7 +3670,7 @@ ReleasePredicateLocks(bool isCommit, bool isReadOnlySafe)
 			 */
 			if (SxactIsDeferrableWaiting(roXact) &&
 				(SxactIsROUnsafe(roXact) || SxactIsROSafe(roXact)))
-				ProcSendSignal(roXact->pid);
+				ProcSendSignal(roXact->pgprocno);
 
 			possibleUnsafeConflict = nextConflict;
 		}
@@ -5006,6 +5007,7 @@ PostPrepare_PredicateLocks(TransactionId xid)
 	Assert(SxactIsPrepared(MySerializableXact));
 
 	MySerializableXact->pid = 0;
+	MySerializableXact->pgprocno = INVALID_PGPROCNO;
 
 	hash_destroy(LocalPredicateLockHash);
 	LocalPredicateLockHash = NULL;
@@ -5081,6 +5083,7 @@ predicatelock_twophase_recover(TransactionId xid, uint16 info,
 		sxact->vxid.backendId = InvalidBackendId;
 		sxact->vxid.localTransactionId = (LocalTransactionId) xid;
 		sxact->pid = 0;
+		sxact->pgprocno = INVALID_PGPROCNO;
 
 		/* a prepared xact hasn't committed yet */
 		sxact->prepareSeqNo = RecoverySerCommitSeqNo;
diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index 2575ea1ca0..a8934fdae8 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -177,8 +177,6 @@ InitProcGlobal(void)
 	ProcGlobal->autovacFreeProcs = NULL;
 	ProcGlobal->bgworkerFreeProcs = NULL;
 	ProcGlobal->walsenderFreeProcs = NULL;
-	ProcGlobal->startupProc = NULL;
-	ProcGlobal->startupProcPid = 0;
 	ProcGlobal->startupBufferPinWaitBufId = -1;
 	ProcGlobal->walwriterLatch = NULL;
 	ProcGlobal->checkpointerLatch = NULL;
@@ -624,21 +622,6 @@ InitAuxiliaryProcess(void)
 	on_shmem_exit(AuxiliaryProcKill, Int32GetDatum(proctype));
 }
 
-/*
- * Record the PID and PGPROC structures for the Startup process, for use in
- * ProcSendSignal().  See comments there for further explanation.
- */
-void
-PublishStartupProcessInformation(void)
-{
-	SpinLockAcquire(ProcStructLock);
-
-	ProcGlobal->startupProc = MyProc;
-	ProcGlobal->startupProcPid = MyProcPid;
-
-	SpinLockRelease(ProcStructLock);
-}
-
 /*
  * Used from bufmgr to share the value of the buffer that Startup waits on,
  * or to reset the value to "not waiting" (-1). This allows processing
@@ -1903,38 +1886,12 @@ ProcWaitForSignal(uint32 wait_event_info)
 }
 
 /*
- * ProcSendSignal - send a signal to a backend identified by PID
+ * ProcSendSignal - send a signal to a backend identified by pgprocno
  */
 void
-ProcSendSignal(int pid)
+ProcSendSignal(int pgprocno)
 {
-	PGPROC	   *proc = NULL;
-
-	if (RecoveryInProgress())
-	{
-		SpinLockAcquire(ProcStructLock);
-
-		/*
-		 * Check to see whether it is the Startup process we wish to signal.
-		 * This call is made by the buffer manager when it wishes to wake up a
-		 * process that has been waiting for a pin in so it can obtain a
-		 * cleanup lock using LockBufferForCleanup(). Startup is not a normal
-		 * backend, so BackendPidGetProc() will not return any pid at all. So
-		 * we remember the information for this special case.
-		 */
-		if (pid == ProcGlobal->startupProcPid)
-			proc = ProcGlobal->startupProc;
-
-		SpinLockRelease(ProcStructLock);
-	}
-
-	if (proc == NULL)
-		proc = BackendPidGetProc(pid);
-
-	if (proc != NULL)
-	{
-		SetLatch(&proc->procLatch);
-	}
+	SetLatch(&ProcGlobal->allProcs[pgprocno].procLatch);
 }
 
 /*
diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h
index 33fcaf5c9a..9b634616e4 100644
--- a/src/include/storage/buf_internals.h
+++ b/src/include/storage/buf_internals.h
@@ -187,7 +187,7 @@ typedef struct BufferDesc
 	/* state of the tag, containing flags, refcount and usagecount */
 	pg_atomic_uint32 state;
 
-	int			wait_backend_pid;	/* backend PID of pin-count waiter */
+	int			wait_backend_pgprocno;	/* backend of pin-count waiter */
 	int			freeNext;		/* link in freelist chain */
 	LWLock		content_lock;	/* to lock access to buffer contents */
 } BufferDesc;
diff --git a/src/include/storage/predicate_internals.h b/src/include/storage/predicate_internals.h
index 104f560d38..f154b3c3b8 100644
--- a/src/include/storage/predicate_internals.h
+++ b/src/include/storage/predicate_internals.h
@@ -113,6 +113,7 @@ typedef struct SERIALIZABLEXACT
 	TransactionId xmin;			/* the transaction's snapshot xmin */
 	uint32		flags;			/* OR'd combination of values defined below */
 	int			pid;			/* pid of associated process */
+	int			pgprocno;		/* pgprocno of associated process */
 } SERIALIZABLEXACT;
 
 #define SXACT_FLAG_COMMITTED			0x00000001	/* already committed */
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index be67d8a861..7c1e2efe30 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -352,9 +352,6 @@ typedef struct PROC_HDR
 	Latch	   *checkpointerLatch;
 	/* Current shared estimate of appropriate spins_per_delay value */
 	int			spins_per_delay;
-	/* The proc of the Startup process, since not in ProcArray */
-	PGPROC	   *startupProc;
-	int			startupProcPid;
 	/* Buffer id of the buffer that Startup process waits for pin on, or -1 */
 	int			startupBufferPinWaitBufId;
 } PROC_HDR;
@@ -395,7 +392,6 @@ extern void InitProcess(void);
 extern void InitProcessPhase2(void);
 extern void InitAuxiliaryProcess(void);
 
-extern void PublishStartupProcessInformation(void);
 extern void SetStartupBufferPinWaitBufId(int bufid);
 extern int	GetStartupBufferPinWaitBufId(void);
 
@@ -411,7 +407,7 @@ extern bool IsWaitingForLock(void);
 extern void LockErrorCleanup(void);
 
 extern void ProcWaitForSignal(uint32 wait_event_info);
-extern void ProcSendSignal(int pid);
+extern void ProcSendSignal(int pgprocno);
 
 extern PGPROC *AuxiliaryPidGetProc(int pid);
 
-- 
2.30.2