alt Hacker NewsAllocation happens. You can leave it to the compiler, the runtime, or let the code control it.
The automatic solutions are usually pretty good and usually the right place to start. But if performance is a priority, you want options.
BTW, “per-frame arena” is part of a general pattern of a repeated interval of work doing significant allocation. This is really common in software of all kinds… servers that process requests (like web servers and database servers) and typical command line tools.
Way back in the aughties I saw an interesting analysis (on a now defunct blog) indicating that under typical usage C# implementations tend to outperform C++ implementations in long-running business applications. The supposed reason was that C#’s compacting GC keeps the cost of new allocations fairly constant. By contrast, in C++ under typical use every new allocation requires probing for a sufficiently large block of free memory in an increasingly fragmented heap.
I haven’t tried to replicate this for myself. And, even assuming for the sake of argument that it was definitely true back then, a lot can happen in 20 years. But still, it does speak to wanting options when performance really is critical.