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mknyszektoday at 12:19 AM1 replyview on HN

I think this is a misunderstanding. If the program out-paces the GC because the GC guessed the trigger point wrong, something has to give.

In Go, what gives is goroutines have to use some of their time slice to assist the GC and pay down their allocations.

In Java, I believe what you used to get was called "concurrent mode failure" which was somewhat notorious, since it would just stop the world to complete the mark phase. I don't know how this has changed. Poking around a little bit it seems like something similar in ZGC is called "allocation failure"?

The GC assist approach adopted by Go was inspired by real-time GC techniques from the literature and in practice it works nicely. It's not perfect of course, but it's worked just fine for lots of programs. From a purely philosophical point of view, I think it results in a more graceful degradation under unexpectedly high allocation pressure than stopping the world, but what happens in practice is much more situational and relies on good heuristics in the implementation.


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adgjlsfhk1today at 12:36 AM

A lot of the answer is that if you can do more work while generating less garbage (lower allocation rate) this problem basically solves itself. Basically every "high performance GC language" other than Java allows for "value type"/"struct"s which allow for way lower allocation rate, which puts a lot less pressure on the GC.

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