[crac] RFR: 8364554: [CRaC] Improve CRaC VM options' docs [v2]

[Timofei Pushkin]

On Mon, 4 Aug 2025 14:27:45 GMT, Radim Vansa <rvansa at openjdk.org> wrote:

>> Timofei Pushkin has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Improve wording for CRaCMinPid
>
> src/hotspot/share/runtime/globals.hpp line 2017:
> 
>> 2015:                                                                             \
>> 2016:   product(bool, CRaCTraceStartupTime, false, DIAGNOSTIC,                    \
>> 2017:           "Trace restore startup time")                                     \
> 
> So "restore" or "startup"? :-) What about
> 
>> Print timestamp after successful restore by CRaC engine
> 
> In general, I think that this should be turned into unified logging configuration option. It's also weird that it is not restore-settable, you have to set that on checkpoint...

Will improve the wording. The name can also be improved but I'll leave it as is for now since maybe the option should be deprecated (see below).

> It's also weird that it is not restore-settable, you have to set that on checkpoint

We cannot really make it restore-settable because the timestamp is printed before restore-settable options are read. Unless we record the timestamp to print it later.

We also have `jdk.crac.trace-startup-time` property used for the same purpose on the Java side (also cannot be changed on restore, although it could be) — we should probably unify these deprecating one of them. If they get unified the VM-level one should continue without the unified logging so that it prints to the same destination as the Java-level one.

Anyway, I'll open a separate task for this as there are thinks to be thought through.

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PR Review Comment: https://git.openjdk.org/crac/pull/256#discussion_r2253541100