From f96708d14ab0073abd95c463eaf8d60db42f411d Mon Sep 17 00:00:00 2001
From: Yuto Hayamizu <y.hayamizu@gmail.com>
Date: Tue, 20 May 2014 16:19:56 +0900
Subject: [PATCH] pre-populating lwlock_stats entries

---
 src/backend/storage/lmgr/lwlock.c |   21 +++++++++++++++++++++
 src/backend/storage/lmgr/proc.c   |    8 ++++++++
 src/include/storage/lwlock.h      |    4 ++++
 3 files changed, 33 insertions(+)

diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c
index d23ac62..fc97ae0 100644
--- a/src/backend/storage/lmgr/lwlock.c
+++ b/src/backend/storage/lmgr/lwlock.c
@@ -359,8 +359,29 @@ CreateLWLocks(void)
 	MainLWLockTranche.array_base = MainLWLockArray;
 	MainLWLockTranche.array_stride = sizeof(LWLockPadded);
 	LWLockRegisterTranche(0, &MainLWLockTranche);
+
+#ifdef LWLOCK_STATS
+	InitializeLWLockStats();
+#endif
 }
 
+#ifdef LWLOCK_STATS
+void
+InitializeLWLockStats(void)
+{
+	int			numLocks = NumLWLocks();
+	int			id;
+	LWLockPadded	*lock;
+
+	if (MyProc == NULL) return;
+
+	/* Initialize all lwlock_stats entries of MainLWLockArray */
+	for (id = 0, lock = MainLWLockArray; id < numLocks; id++, lock++)
+	{
+		get_lwlock_stats_entry(&lock->lock);
+	}
+}
+#endif
 
 /*
  * LWLockAssign - assign a dynamically-allocated LWLock number
diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index 266b0da..e09cbf8 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -415,6 +415,10 @@ InitProcess(void)
 	 * the deadlock checker.
 	 */
 	InitDeadLockChecking();
+
+#ifdef LWLOCK_STATS
+	InitializeLWLockStats();
+#endif
 }
 
 /*
@@ -566,6 +570,10 @@ InitAuxiliaryProcess(void)
 	 * Arrange to clean up at process exit.
 	 */
 	on_shmem_exit(AuxiliaryProcKill, Int32GetDatum(proctype));
+
+#ifdef LWLOCK_STATS
+	InitializeLWLockStats();
+#endif
 }
 
 /*
diff --git a/src/include/storage/lwlock.h b/src/include/storage/lwlock.h
index 175fae3..f0f1c21 100644
--- a/src/include/storage/lwlock.h
+++ b/src/include/storage/lwlock.h
@@ -209,6 +209,10 @@ extern int	LWLockNewTrancheId(void);
 extern void LWLockRegisterTranche(int, LWLockTranche *);
 extern void LWLockInitialize(LWLock *, int tranche_id);
 
+#ifdef LWLOCK_STATS
+extern void InitializeLWLockStats(void);
+#endif
+
 /*
  * Prior to PostgreSQL 9.4, we used an enum type called LWLockId to refer
  * to LWLocks.  New code should instead use LWLock *.  However, for the
-- 
1.7.10.4