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by cogman10 1495 days ago
Not on the first go around. AFAIK, they are looking at exposing more of the internal scheduling API but that's likely not going to be a part of the initial release.

The executor services referred to in the blog are for the order of execution of tasks on the virtual thread pool. For a "virtualThreadExecutor" service, every task will get a virtual thread and scheduling will happen internally.

You can still use a fixed thread pool with a custom task scheduler if you like, but probably not exactly what you are after.
1 comments
CHY872 1495 days ago
This blogpost does rely on plugging in an executor. While the API was removed, it’s one private variable away (documented in footnote). As you say, it seems like it’s an ‘on the way, but later’ thing - the last Loom preview I used (a while ago) actually had the API so when I started drafting this post I was unhappily surprised!
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pron 1495 days ago
Right, custom schedulers aren't quite ready for release yet -- there's a small missing piece in the VM that's required to fully preserve the spec, and they need a lot of testing that we don't yet have -- so we decided to go ahead without them and add them later.
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CHY872 1495 days ago
What’s the missing piece?
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pron 1494 days ago
A technical detail. Monitors (synchronized) record their owners as the OS thread, which makes the VM not know whether the carrier or the virtual thread owns a monitor, as they both share the same OS thread.
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CHY872 1493 days ago
For any future readers, I think this is the bug: https://bugs.openjdk.java.net/browse/JDK-8281642
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cogman10 1495 days ago
IMO, they are focusing on the right thing here. Getting a good virtual thread API GA will be paramount in the decisions around scheduling and continuations in the future.

Maybe a little disappointing for low level nuts and other languages like kotlin, but the right move IMO. Virtual threads alone will be a huge benefit to the ecosystem. The other stuff will help, but won't have near the same impact.

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CHY872 1495 days ago
Agreed. And the pluggable scheduling is still a key part of it, just doesn’t need to be a thing to get right out of the gate. I’m honestly mega excited that Loom is even a real thing that exists and that you can use.
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