[crac] RFR: Resize ForkJoinPool and some concurrent data structures

[Dan Heidinga]

On Mon, 27 Mar 2023 12:37:41 GMT, Anton Kozlov <akozlov at openjdk.org> wrote:

> From a purely technical point of view, backporting those changes from upstream provides the CRaC implementation better understood, tested, etc.
> 

+1

> Imaging we have a space like crac-17u (jdk17u with CRaC changes), and a policy allowing backporting something extra compared to jdk17u, would we need a special CRaC version to resize FJP or backports would be enough?

I think the backports would cover the tricky changes to FJP though we'd still need a JDKResrouce::{beforeCheckpoint, afterCheckpoint} implementation.

An ::afterCheckpoint method to call ::setParallelism to match the number of cpu's on the restored system.  The ::beforeCheckpoint implementation could be used to resize the pool to an expected number of cpus (default 4?) as an optional optimization.

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PR Comment: https://git.openjdk.org/crac/pull/54#issuecomment-1485067770