3 ms·

Haskell, Java

• jeremyjh 4mo ago
  Java and Crystal are not equivalent - neither have preemptible threads. Lots of other languages have co-routines or other cooperative systems - async/await are really just variants of that. I didn't check if Gossamer is actually preemptible. I believe the short list of production languages with preemptible M:N schedulers are limited to: Erlang/Elixir Haskell Go
  • msgilligan 4mo ago
    Java threads including Virtual Threads (JDK 21+) are preemptive.
    • jeremyjh 4mo ago
      They are not - and do not claim to be preemptive. They claim they are "not cooperative", but even that doesn't mean what anyone else thinks it means. This paragraph is the only one containing the word "preempt" in JEP 444: "The scheduler does not currently implement time sharing for virtual threads. Time sharing is the forceful preemption of a thread that has consumed an allotted quantity of CPU time. While time sharing can be effective at reducing the latency of some tasks when there are a relatively small number of platform threads and CPU utilization is at 100%, it is not clear that time sharing would be as effective with a million virtual threads." https://openjdk.org/jeps/444 https://openjdk.org/jeps/444
      • gf000 4mo ago
        How did we get to that? We were talking about n:m threading, especially with threads being blocking IO-aware, being able to automagically turning such a call to non-blocking. Java more than fits that description.
        • jeremyjh 4mo ago
          The original message you replied to said (mistakenly): > adopt true goroutines Goroutines are preemptive. The distinction between cooperative and non-cooperative concurrency is very significant - it is the difference between never having to think about the scheduler and always having to thinking about it when doing CPU intensive tasks.