日志文件中奇怪的Mongo DB writelock值

我在我的MongoDB日志文件中得到了一些奇怪的writelock值：

Wed Mar 19 10:03:47.007 [snapshotthread] cpu: elapsed:4010 writelock: 0% Wed Mar 19 10:03:51.007 [snapshotthread] cpu: elapsed:4000 writelock: 0% Wed Mar 19 10:03:55.012 [snapshotthread] cpu: elapsed:4005 writelock: 0% Wed Mar 19 10:03:59.028 [snapshotthread] cpu: elapsed:4015 writelock: 385% Wed Mar 19 10:04:03.042 [snapshotthread] cpu: elapsed:4014 writelock: -2147483648% Wed Mar 19 10:04:07.045 [snapshotthread] cpu: elapsed:4003 writelock: 0% 

这是“正常”还是应该担心？