The JVM can relocate memory to avoid fragmentation. Rust can't, at least natively. Are they not worried about this regression?
Well Java need it because it fragments memory a lot. With Rust one has value types and stack allocation which takes care of one of the biggest cause of fragmentation.
Writing code that would not fragment memory over time is arguable much harder than writing GC friendly code.
I haven't found that to be the case in my experience: just for example in java you tend to end up with essentially a lot of `Vec<Box<Thing>>` which causes a lot of fragmentation. In rust you tend to end up with `Vec<Thing>` where `Thing`s are inlined. (And replace Vec with the stack for the common case). I find it more like Java is better at solving a problem it created by making everything an object.
Yeah, cooking food in kitchen is much harder than having it delivered from restaurant at doorstep.
Reasonable people will see if cost makes it worthwhile.
With 10x the throughput (TPS) and the lack of GC pauses (which were the cause of the rewrite), how would they measure such a regression, let alone worry about it?