Amazon EC2 Spot now allows Amazon EBS-backed instances to be stopped in the event of interruption, instead of being terminated when capacity is no longer available at your preferred price. Spot can then fulfill your request by restarting instances from a stopped state when capacity is available within your price and time requirements.
用法是把 Spot Instance 的關機設定設為 Stop：
To use this new feature, choose “stop” instead of “terminate” as the interruption behavior when submitting a persistent Spot request. When you choose “stop”, Spot will shut down your instance upon interruption.
恢復的時候就會儘量保持一樣地開回來 (連 instance id 都相同)：
When capacity is available again within your price and time requirements, Spot will restart your instance. Upon restart, the EBS root device is restored from its prior state, previously attached data volumes are reattached, and the instance retains its instance ID.
As of Go 1.7, the one remaining source of unbounded and potentially non-trivial stop-the-world (STW) time is stack re-scanning.
然後拿新的解法來戰，目前初步的測試看起來可以降到 50µs (== 0.05ms)：
We propose to eliminate the need for stack re-scanning by switching to a hybrid write barrier that combines a Yuasa-style deletion write barrier [Yuasa '90] and a Dijkstra-style insertion write barrier [Dijkstra '78]. Preliminary experiments show that this can reduce worst-case STW time to under 50µs, and this approach may make it practical to eliminate STW mark termination altogether.
The high level summary is that this reduces worst-case STW time to about 100 µs and typical 95%ile STW time to 50 µs (assuming, of course, that the OS doesn't get in the way and that the system isn't otherwise overloaded).