[ncmncm]

There is a fair bit of C++ code in use. We have no need to guess.

And, the answer is that real programs in obligate-GC languages spend overwhelmingly more time in GC than C++ or Rust. Much of this time is spent waiting on cache misses, which are hard to track to the responsible bit of code.

[weberc2]

Do you have evidence for this? Specifically C++ and Rust tend to be written for applications where tight control over memory is necessary and so any sample like you're describing is going to be biased by these carefully tuned C++/Rust applications. Even the standard libraries for C++ and Rust differ considerably in allocation behavior from Java or Python--these languages are conventionally designed to allocate differently, but that doesn't mean that the GC is the problem. Further, different programming paradigms allocate memory differently and the distribution of these paradigms across GC languages and non-GC languages (or whatever terms you like) are almost certainly varied. There are lots of confounding variables to control for, and until you control for them you're pretty much just guessing.

[nicoburns]

I think it's pretty obvious if you use these languages. A lot of things that require you to heap allocate in Java or Python (like classes!) have stack-allocated versions in rust/c++. Which means that code which avoids slow heap allocation is much nicer than equiavlent code in Java that must avoid high level abstractions.

You're right that the GC isn't necessarily the issue. It's more the forced heap allocation which most GC languages come with.

[weberc2]

Agreed, although to pick a nit (because it's an interesting nit IMO) "Classes" is orthogonal to allocation. In C++ you choose where you allocate your class and in Java the escape analyzer chooses for you. C# and Go have a GC and (more or less) semantics for heap-vs-stack allocation.

[xfer]

That heap allocation is most likely either optimized away and allocated in stack/ allocated in minor heap which is same as bumping a pointer just like in stack!

[weberc2]

Only for Java, not Python. And in any case, the cache performance will still be worse, but that’s a more minor cost.