diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
new file mode 100755
index 1c41428..61fc1e6
*** a/src/backend/storage/buffer/bufmgr.c
--- b/src/backend/storage/buffer/bufmgr.c
*************** PinBuffer(volatile BufferDesc *buf, Buff
*** 1105,1111 ****
  		}
  		else
  		{
! 			if (buf->usage_count == 0)
  				buf->usage_count = 1;
  		}
  		result = (buf->flags & BM_VALID) != 0;
--- 1105,1111 ----
  		}
  		else
  		{
! 			if (buf->usage_count <= 0)
  				buf->usage_count = 1;
  		}
  		result = (buf->flags & BM_VALID) != 0;
*************** SyncOneBuffer(int buf_id, bool skip_rece
*** 1665,1671 ****
  	 */
  	LockBufHdr(bufHdr);
  
! 	if (bufHdr->refcount == 0 && bufHdr->usage_count == 0)
  		result |= BUF_REUSABLE;
  	else if (skip_recently_used)
  	{
--- 1665,1671 ----
  	 */
  	LockBufHdr(bufHdr);
  
! 	if (bufHdr->refcount == 0 && bufHdr->usage_count <= 0)
  		result |= BUF_REUSABLE;
  	else if (skip_recently_used)
  	{
diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
new file mode 100755
index c76aaf7..faa8523
*** a/src/backend/storage/buffer/freelist.c
--- b/src/backend/storage/buffer/freelist.c
*************** StrategyGetBuffer(BufferAccessStrategy s
*** 178,184 ****
  		 * we'd better check anyway.)
  		 */
  		LockBufHdr(buf);
! 		if (buf->refcount == 0 && buf->usage_count == 0)
  		{
  			if (strategy != NULL)
  				AddBufferToRing(strategy, buf);
--- 178,184 ----
  		 * we'd better check anyway.)
  		 */
  		LockBufHdr(buf);
! 		if (buf->refcount == 0 && buf->usage_count <= 0)
  		{
  			if (strategy != NULL)
  				AddBufferToRing(strategy, buf);
*************** StrategyGetBuffer(BufferAccessStrategy s
*** 201,209 ****
  
  		/*
  		 * If the buffer is pinned or has a nonzero usage_count, we cannot use
! 		 * it; decrement the usage_count (unless pinned) and keep scanning.
  		 */
- 		LockBufHdr(buf);
  		if (buf->refcount == 0)
  		{
  			if (buf->usage_count > 0)
--- 201,211 ----
  
  		/*
  		 * If the buffer is pinned or has a nonzero usage_count, we cannot use
! 		 * it; decrement the usage_count (unless pinned) and keep scanning.  The
! 		 * buffer header is deliberately not locked during the initial examination
! 		 * of refcount or while usage_count is adjusted in order to minimize
! 		 * spinlock contention while holding the BufFreelistLock.
  		 */
  		if (buf->refcount == 0)
  		{
  			if (buf->usage_count > 0)
*************** StrategyGetBuffer(BufferAccessStrategy s
*** 213,222 ****
  			}
  			else
  			{
! 				/* Found a usable buffer */
! 				if (strategy != NULL)
! 					AddBufferToRing(strategy, buf);
! 				return buf;
  			}
  		}
  		else if (--trycounter == 0)
--- 215,227 ----
  			}
  			else
  			{
! 				/* Found a usable buffer. But is it truly unpinned? */
! 				if (TryLockBufHdr(buf))
! 				{
! 					if (strategy != NULL)
! 						AddBufferToRing(strategy, buf);
! 					return buf;
! 				}
  			}
  		}
  		else if (--trycounter == 0)
*************** StrategyGetBuffer(BufferAccessStrategy s
*** 228,237 ****
  			 * probably better to fail than to risk getting stuck in an
  			 * infinite loop.
  			 */
- 			UnlockBufHdr(buf);
  			elog(ERROR, "no unpinned buffers available");
  		}
- 		UnlockBufHdr(buf);
  	}
  }
  
--- 233,240 ----
diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h
new file mode 100755
index f0e5144..943215c
*** a/src/include/storage/buf_internals.h
--- b/src/include/storage/buf_internals.h
*************** typedef struct sbufdesc
*** 168,173 ****
--- 168,174 ----
   */
  #define LockBufHdr(bufHdr)		SpinLockAcquire(&(bufHdr)->buf_hdr_lock)
  #define UnlockBufHdr(bufHdr)	SpinLockRelease(&(bufHdr)->buf_hdr_lock)
+ #define TryLockBufHdr(bufHdr)	TrySpinLockAcquire(&(bufHdr)->buf_hdr_lock)
  
  
  /* in buf_init.c */
diff --git a/src/include/storage/spin.h b/src/include/storage/spin.h
new file mode 100755
index f459b90..ed68318
*** a/src/include/storage/spin.h
--- b/src/include/storage/spin.h
***************
*** 63,68 ****
--- 63,70 ----
  
  #define SpinLockAcquire(lock) S_LOCK(lock)
  
+ #define TrySpinLockAcquire(lock)	!(TAS_SPIN(lock))
+ 
  #define SpinLockRelease(lock) S_UNLOCK(lock)
  
  #define SpinLockFree(lock)	S_LOCK_FREE(lock)