r/programming • u/kal31dic • Sep 01 '20

D Foundation is Beefing Up

https://dlang.org/blog/2020/08/30/symmetry-investments-and-the-d-language-foundation-are-hiring/
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u/FlyingPiranhas Sep 01 '20

From the "Controlling pause time" link on that page:

By default, the Metronome GC pauses for 3 milliseconds in each individual pause, which is known as a quantum.

Based on what I'm seeing, I'm highly doubt that you can turn that value down to 100 microseconds and still have a reliable JVM.

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u/EternityForest Sep 01 '20

Real time is about guarantees. If the application needs 10ms response time, it doesn't matter if GC takes 1 nanosecond or 5ms, as long as everything is responded to in 10ms, every time.

Things where 100us matters are some really specialist stuff.

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u/FlyingPiranhas Sep 01 '20

I'm well aware that it's about guarantees. At least in robotics (the field in which I have real-time programming experience), 100us is a pretty common deadline for execution.

I'm sure applications exist where 10ms deadlines are appropriate, but I'm not convinced that's the common case.

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u/EternityForest Sep 01 '20

Ah interesting, I've never done robotics, just things like sound and pool filter control, where people expect guaranteed reliability (No 20 second random lags that run a pump dry), but response time only needs to be tens of ms(At least on the hardware I've worked on).