Rust used to use jemalloc as the default, but went back to using the system malloc back in 2018-ish[0]. Since Rust now has the GlobalAlloc trait (and the #[global_allocator] attribute), apps can use jemalloc as their allocator if they want. Not sure if there's a way for users to override via LD_PRELOAD or something, though.
It turns out jemalloc isn't always best for every workload and use case. While the system allocator is often far from perfect, it at least has been widely tested as a general-purpose allocator.
It turns out jemalloc isn't always best for every workload and use case. While the system allocator is often far from perfect, it at least has been widely tested as a general-purpose allocator.
[0] https://github.com/rust-lang/rust/issues/36963