Although we add [hot_peer_cache](https://github.com/pingcap/pd/blob/92e29af8378f43b3555cf7c266ef020010825597/server/statistics/hot_peer_cache.go#L119) and TimeMedian, which is a combination of [AverageOverTime](https://github.com/pingcap/pd/blob/92e29af8378f43b3555cf7c266ef020010825597/server/statistics/avg_over_time.go#L37) and [Median Moving Average](https://github.com/pingcap/pd/blob/92e29af8378f43b3555cf7c266ef020010825597/server/statistics/avg_over_time.go#L37), there are still some jitter sometimes. 