[crac] RFR: Decouple JVM and CRIU [v2]

[Dan Heidinga]

On Thu, 28 Oct 2021 19:23:07 GMT, Anton Kozlov <akozlov at localhost> wrote:

>> CREngine option to specify a program to do checkpoint/restore.
>> * `criuengine` to use CRIU as it was used before.
>> * `pauseengine` that stores PID in a file and pauses JVM until `java -XX:CRaCRestoreFrom=` is called. This should allow external mechanisms that may operate on a process.
>> * `simengine` is something that simulates restore immediately, with the same effect as `-XX:+CRAllowToSkipCheckpoint`. It is intended to be simplest example and could be a starting point to implement Checkpoint/Restore with e.g. the help of a VM/container/... in which JVM is running.
>
> Anton Kozlov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix reviewer's notes

Sorry for delay circling back to this - overall, change looks reasonable

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Marked as reviewed by DanHeidinga at github.com (no known OpenJDK username).

PR: https://git.openjdk.java.net/crac/pull/3