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by cbsmith 1800 days ago
Java had M:N green thread models a LOOOOONG time ago.

And Linux tried M:N thread implementations specifically to improve thread performance.

In both cases, it turned out that just using 1:1 native threads ended up being a net win.
1 comments
hawk_ 1800 days ago
i am not aware of M:N thread builtin in Java even from long time ago, at least not in a way that you could control N
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cbsmith 1800 days ago
The old JDK 1.1 Developer's Guide had a page on the different thread models: https://docs.oracle.com/cd/E19455-01/806-3461/6jck06gqk/inde...

At the time, Solaris had the only "certified" JVM that did M:N threads, so they really liked to make a big deal about it.

You could control N through a JNI call to thr_setconcurrency. Not portable, but it worked. That particular capability was almost always not helpful.

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truffdog 1800 days ago
It was Solaris only, so there is definitely an asterisk somewhere.
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cbsmith 1800 days ago
It was all very long ago, but the NGPT project did M:N threading on Linux (https://web.archive.org/web/20020408103057/http://www-124.ib...).

There were also a number of M:N JVM implementations that were particularly popular in the soft-realtime space back in the early 2000's.

One of the fun trends with computing is that as hardware, software, and applications evolve, ideas that were once not terribly useful suddenly become useful again. It's entirely possible that M:N threads for the JVM is one of those cases, but it's NOT a new idea.

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