When "Good Enough" Isn't: The Story Behind a Custom Memory Manager for the Nintendo DS
Years ago, I found myself deep in the weeds of developing a top-down, bullet hell shooter for the Nintendo DS. The studio I joined had a veteran engine — robust from years of shipping titles — but the DS was new territory for this company, and it brought more than a few surprises. My job was to squeeze everything we could out of its limited hardware and make our designer’s creative chaos come to life.
Things started smoothly: I optimized rendering pipelines, streamlined low-level code, and, working alongside a designer obsessed with bullet hell games, helped build a scripting language for enemies and bullets so he could spin up new patterns and behaviors with ease. For a while, it was development bliss.
Then we turned the chaos dial up — and everything ground to a halt. The designer wanted screens awash in hundreds of projectiles and enemies. When we tried it, the system choked: framerate dropped, input lagged, and the game lost all sense of bullet hell thrill. I was tasked with diagnosing the problem and fixing it.
Finding the Bottleneck
So, I took to profiling the code, and the core problem quickly stood out: memory allocation. Every on-screen burst, every enemy or bullet, every effect — each required a fresh memory allocation. On the DS’s limited hardware, this quickly became unsustainable. Dynamic memory allocation is often a bottleneck, and this game was no exception. Allocator overhead and fragmentation exploded under so many rapid, tiny allocations and deallocations.
Classic fixes like object pools or preallocation crossed my mind, but I knew they’d force hard caps or design limits that felt at odds with the spirit of bullet hell, and with the creative freedom our designer relished. The solution had to be flexible, fast, and invisible to the creative process. I wanted to give the designer the freedom to create as much chaos as he wanted, without worrying about the performance implications.
Building a Custom Memory Manager
So, I decided to do the unthinkable: rewrite the memory manager from scratch, in the heart of a mature, “if it ain’t broke, don’t fix it” engine.
The structure was built around two core doubly linked lists:
- Unallocated memory: Nodes kept in memory order, each with a fixed-size header immediately preceding its corresponding free block. That constant offset made searching, splitting, and merging reliable and performant. Allocations could be pulled from the start or end of the pool — allowing for long-lived data at one end and high-velocity, short-lived objects at the other, which fit the game’s “waves of chaos” memory use perfectly.
- Allocated memory: Managed as a stack, with headers tracking allocations in allocation order. Since most deallocations in a real-time action game happened last-in, first-out, this made freeing blocks exceptionally fast.
When deallocating, a block returned to the unallocated list and triggered a coalescing pass: any physically adjacent free nodes were merged into one. In an ideal run, fragmentation faded away as the list shrank back to just a handful — or even a single — large free node.
The Impact
Performance soared. The manager’s design slashed overhead, sped up allocations and deallocations, and kept fragmentation at bay — even at the peak of on-screen chaos. The designer was able to crank up his creative ambitions without constraints, and the game ran at full speed. That memory manager didn’t just solve our immediate problem — it became the studio’s standard for future projects, a small codebase with a big legacy.
Sometimes the biggest breakthroughs don’t come from building new features — but from questioning and revisiting the foundations themselves. “Good enough” wasn’t good enough for what we wanted to achieve. By rethinking memory management, we unlocked the speed and creative power needed to do something remarkable on hardware that, at first glance, couldn’t handle it.
Working on a project where “good enough” might not be enough? Let’s talk - I can help you make the tough calls.