Why async fn in traits are hard

Re:Why async fn in traits are hard by steveklabnik on Sunday October 27, 2019 @02:34PM (#21371556)

As always, it depends on a lot of details. A generational garbage collector can be made to allocate extremely quickly; IIRC for the JVM it's like, seven instructions? For short lived allocations, it sort of acts like an arena, which is very high performance. malloc/free need to be quite general.

It's always about details though. If a GC is faster than malloc/free, but your language doesn't tend to allocate much to begin with, the whole system can be faster even if malloc is slower. It always depends.

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Re:Why async fn in traits are hard by geogriffin on Sunday October 27, 2019 @10:21PM (#21373777)

Doesn't something like jemalloc basically give you this, but without pauses? Thread-local freelists for quick recycling of small allocations without synchronization.. funnily enough, jemalloc even uses some garbage collection mechanisms internally.

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Re:Why async fn in traits are hard by steveklabnik on Monday October 28, 2019 @07:26AM (#21375957)

I don't know a ton about jemalloc internals, but it is true that a lot of modern mallocs use some mechanisms similar to GCs. There's some pretty major constraint differences though.

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