Ephemeral threads

[Michal Domagala]

I would share my reflections
1. All "system" VT, "system" means f.e.created  by Structured Concurrency,
automatically ends and never become unreachable
2. Only application VT can become unreachable, f.e. when a blocking queue
became unreachable
3. Every VT is naturally GC-able, because only diagnostic flag
trackAllThreads saves unreached VT from release
4. Diagnostic is important
5. If trackAllThreads use weak reference, it can impact GC, as
potentially there can be millions of VT

Maybe it is worth to consider `Thread.ofEphemeral()` tracked by weak
reference
1. Implementation effort is minimal, there will be two maps of VT instead
of one
2. Performance effort is zero, because only intentional, application VT can
increase GC time (Volenti non fit iniuria)
3. Diagnostic still works

Regards
Michal Domagala

pon., 12 sty 2026 o 13:41 Alan Bateman <alan.bateman at oracle.com> napisał(a):

>
>
> On 10/01/2026 15:55, Alex Miller wrote:
> > What is the likely future of the trackAllThreads flag?
> TBD. It's clearly an attractive nuisance right now and setting it to
> false is specific to the root "thread grouping". There is some
> performance work required in that area but otherwise I think it needs to
> be removed.
>
> -Alan
>
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