[crac] RFR: 8367975: [CRaC] Pattern in CRaCCheckpointTo

[Radim Vansa]

On Mon, 22 Sep 2025 15:02:24 GMT, Timofei Pushkin <tpushkin at openjdk.org> wrote:

>> Add support for pattern in `CRaCCheckpointTo` VM option.
>
> src/hotspot/share/runtime/crac.cpp line 198:
> 
>> 196:             buf += ret;
>> 197:             buflen -= ret;
>> 198:           } // otherwise just empty string
> 
> I think we should print a warning otherwise

I don't think so; `cpu_features_binary` will return false on `aarch64`, and I don't think the user has to use different patterns to checkpoint on different architectures.

> src/hotspot/share/runtime/crac.cpp line 203:
> 
>> 201:       case 'u': { // Random UUID (v4)
>> 202:           check_no_width();
>> 203:           *fixed = false; // FIXME?
> 
> Looks correct to me, what would you want to fix?

The UUID could be generated once on the first pattern interpolation. Probably needs to be reset on restore, then, to keep the semantic (UUID should change on each checkpoint - that shall be documented, too).

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PR Review Comment: https://git.openjdk.org/crac/pull/264#discussion_r2372146904
PR Review Comment: https://git.openjdk.org/crac/pull/264#discussion_r2372154917