Arenas is one of those patterns that very easy to underestimate. I didn't know about it when I started programming and I run into huge performance issue where I needed to deallocate a huge (sometimes tens of GBs consisting of millions of objects) structure just to make a new one. It was often faster to kill the process and start a new one but that had other downsides. At some point we added a simple hand written arena-like allocator and used it along with malloc. The arena was there for objects on that big structure that will all die at the same point and malloc was for all the other things.

The speed-up was impossible to measure because deallocation that used to take up to 30 seconds (especially after repeat cycles of allocating/deallocating) was now instant.

Even though we had very little experience it was trivial to do in C. Imo it's critical for performance oriented language to make using multiple allocators convenient. GC is a known performance killer but so is malloc in some circumstances.