*** a/src/backend/storage/buffer/bufmgr.c
--- b/src/backend/storage/buffer/bufmgr.c
***************
*** 1674,1685 **** SyncOneBuffer(int buf_id, bool skip_recently_used)
  		return result;
  	}
  
! 	if (!(bufHdr->flags & BM_VALID) || !(bufHdr->flags & BM_DIRTY))
  	{
  		/* It's clean, so nothing to do */
  		UnlockBufHdr(bufHdr);
  		return result;
  	}
  
  	/*
  	 * Pin it, share-lock it, write it.  (FlushBuffer will do nothing if the
--- 1674,1703 ----
  		return result;
  	}
  
! 	if (!(bufHdr->flags & BM_VALID))
  	{
  		/* It's clean, so nothing to do */
  		UnlockBufHdr(bufHdr);
  		return result;
  	}
+ 	else if (!(bufHdr->flags & BM_DIRTY))                                   
+  	{
+  		/*
+  		 * It's clean, so nothing to flush;
+  		 * if buffer is unused then move it to freelist
+  		 */
+  		if (bufHdr->refcount == 0 && bufHdr->usage_count == 0)
+  		{
+  		    UnlockBufHdr(bufHdr);
+  			StrategyMoveBufferToFreeListEnd (bufHdr);
+  		}
+  		else
+  		{                                                   
+  			UnlockBufHdr(bufHdr);
+  		}                  
+  		return result;
+  	}                                                             
+ 
  
  	/*
  	 * Pin it, share-lock it, write it.  (FlushBuffer will do nothing if the
***************
*** 1693,1698 **** SyncOneBuffer(int buf_id, bool skip_recently_used)
--- 1711,1730 ----
  	LWLockRelease(bufHdr->content_lock);
  	UnpinBuffer(bufHdr, true);
  
+ 	/*
+  	 * check if buffer is not used actively by any backend, then move it to freelist
+  	 */
+  	LockBufHdr(bufHdr);            
+  	if (bufHdr->refcount == 0 && bufHdr->usage_count == 0)
+  	{                                          
+  		UnlockBufHdr(bufHdr);                    
+  		StrategyMoveBufferToFreeListEnd (bufHdr);
+  	}                                                                           
+  	else
+  	{                                          
+  		UnlockBufHdr(bufHdr);
+  	}
+ 
  	return result | BUF_WRITTEN;
  }
  
*** a/src/backend/storage/buffer/freelist.c
--- b/src/backend/storage/buffer/freelist.c
***************
*** 259,264 **** StrategyFreeBuffer(volatile BufferDesc *buf)
--- 259,298 ----
  }
  
  /*
+  * StrategyMoveBufferToFreeListEnd: put a buffer on the end of freelist
+  */                                                                                      
+ void
+ StrategyMoveBufferToFreeListEnd(volatile BufferDesc *buf)                                
+ {
+ 	LWLockAcquire(BufFreelistLock, LW_EXCLUSIVE);                                    
+                                                                                          
+  	/*
+  	 * It is possible that we are told to put something in the freelist that
+  	 * is already in it; don't screw up the list if so.
+  	 */                    
+  	if (buf->freeNext == FREENEXT_NOT_IN_LIST)
+  	{                   
+  		/*
+  		 * put the buffer on end of list and if list is empty then
+  		 * assign first and last freebuffer with this buffer id.             
+  		 */     
+  		buf->freeNext = FREENEXT_END_OF_LIST;
+  		if (StrategyControl->firstFreeBuffer < 0)                                
+  		{                
+  			StrategyControl->firstFreeBuffer = buf->buf_id;
+  			StrategyControl->lastFreeBuffer = buf->buf_id;                   
+  			LWLockRelease(BufFreelistLock);              
+  			return;                      
+  		}                                                         
+  		BufferDescriptors[StrategyControl->lastFreeBuffer].freeNext = buf->buf_id;
+  		StrategyControl->lastFreeBuffer = buf->buf_id;
+  	}         
+                                                                                          
+  	LWLockRelease(BufFreelistLock);
+ }                                                                                        
+ 
+ 
+ /*
   * StrategySyncStart -- tell BufferSync where to start syncing
   *
   * The result is the buffer index of the best buffer to sync first.
*** a/src/include/storage/buf_internals.h
--- b/src/include/storage/buf_internals.h
***************
*** 185,190 **** extern BufferDesc *LocalBufferDescriptors;
--- 185,191 ----
  extern volatile BufferDesc *StrategyGetBuffer(BufferAccessStrategy strategy,
  				  bool *lock_held);
  extern void StrategyFreeBuffer(volatile BufferDesc *buf);
+ extern void StrategyMoveBufferToFreeListEnd(volatile BufferDesc *buf);
  extern bool StrategyRejectBuffer(BufferAccessStrategy strategy,
  					 volatile BufferDesc *buf);