diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c
index 0679eb5..10ee364 100644
--- a/src/backend/storage/lmgr/lwlock.c
+++ b/src/backend/storage/lmgr/lwlock.c
@@ -451,9 +451,11 @@ CreateLWLocks(void)
  * LWLockAssign - assign a dynamically-allocated LWLock number
  *
  * We interlock this using the same spinlock that is used to protect
- * ShmemAlloc().  Interlocking is not really necessary during postmaster
- * startup, but it is needed if any user-defined code tries to allocate
- * LWLocks after startup.
+ * ShmemAlloc().  Interlocking is not necessary during postmaster startup, but
+ * it is needed if any user-defined code tries to allocate LWLocks after
+ * startup. Since we allocate large amounts of LWLocks for the buffer pool, we
+ * avoid taking the spinlock when not needed, as it has shown to slowdown
+ * startup considerably.
  */
 LWLock *
 LWLockAssign(void)
@@ -464,14 +466,17 @@ LWLockAssign(void)
 	volatile int *LWLockCounter;
 
 	LWLockCounter = (int *) ((char *) MainLWLockArray - 3 * sizeof(int));
-	SpinLockAcquire(ShmemLock);
+	if (IsUnderPostmaster)
+		SpinLockAcquire(ShmemLock);
 	if (LWLockCounter[0] >= LWLockCounter[1])
 	{
-		SpinLockRelease(ShmemLock);
+		if (IsUnderPostmaster)
+			SpinLockRelease(ShmemLock);
 		elog(ERROR, "no more LWLocks available");
 	}
 	result = &MainLWLockArray[LWLockCounter[0]++].lock;
-	SpinLockRelease(ShmemLock);
+	if (IsUnderPostmaster)
+		SpinLockRelease(ShmemLock);
 	return result;
 }