On 21/05/14 09:19 AM, Zoltán Tóth wrote: > Daniel Micay <danielmi...@gmail.com <mailto:danielmi...@gmail.com>> wrote: > > ... the default > allocator, which is jemalloc right now. > > > Rust's memory management is still under-documented in the manual. I have > a question which have been bothering me for a while. I may have > misunderstood something basic. > > Jemalloc AFAIK synchronizes the allocations, as it is multithread-ready. > However does Rust not use task-specific heaps? [I thought that most of > the dynamic allocations happen in task-specific heaps.] For those is > Jemalloc's synchronization not an unnecessary waste of processor time?
Types like `Vec<T>` and `Box<T>` can be sent between tasks and `Arc<T>` can be shared so there's no task-local heap. It's true that a few types like `Rc<T>` are task-local but there would be no performance gain from an extra layer. It would just create needless memory fragmentation. jemalloc creates 4 arenas for every core (each with a lock) and assigns threads to these arenas. It then has thread local caches on top of those.
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