14 ms·

Is there a concise timelime/history of this? I thought jemalloc was 100% open source, why is Meta in control of it?

masklinn 7mo ago
Jason Evans (the creator of jemalloc) recounted the entire thing last year: https://jasone.github.io/2025/06/12/jemalloc-postmortem/ https://jasone.github.io/2025/06/12/jemalloc-postmortem/
- vintermann 7mo ago
  "Were I to reengage, the first step would be at least hundreds of hours of refactoring to pay off accrued technical debt." Facebook's coding AIs to the rescue, maybe? I wonder how good all these "agentic" AIs are at dreaded refactoring jobs like these.
  - xxs 7mo ago
    Refactor doesn't mean just artificial puff-up jobs, it's very likely internal changes and reorganization (hence 100s of hours). There are not many engineers capable of working on memory allocators, so adding more burden by agentic stuff is unlikely to produce anything of value.
  - rvz 7mo ago
    > Facebook's coding AIs to the rescue, maybe? I wonder how good all these "agentic" AIs are at dreaded refactoring jobs like these. No. This is something you shouldn't allow coding agents anywhere near, unless you have expert-level understanding required to maintain the project like the previous authors have done without an AI for years.
    - kenferry 7mo ago
      Hm, I wonder. I've done some work in this sort of area before, though not literally on a malloc. Yes you very much want to be careful, but ultimately it's the tests that give you confidence. Pound the heck out of it in multithreaded contexts and test for consistency.
      - vlovich123 7mo ago
        AI is more than happy to declare the test wrong and “fix it” if you’re not careful. And the cherry on top is that sometimes the test could be wrong or need updating due to changed behavior. So…
      - rvz 7mo ago
        > ...but ultimately it's the tests that give you confidence. Pound the heck out of it in multithreaded contexts and test for consistency. I don't think so. Even on LLM generated code, it is still not enough and you cannot trust it. They can pass the tests and still cause a regression and the code will look seemingly correct, for example in this case study [0]. [0] https://sketch.dev/blog/our-first-outage-from-llm-written-code https://sketch.dev/blog/our-first-outage-from-llm-written-co...
echelon 7mo ago
If you filter the commits to the past five years, four of the top six committers are Meta employees. The other two might be as well, it just doesn't say that on their Github / personal website.

Jason Evans (the creator of jemalloc) recounted the entire thing last year: https://jasone.github.io/2025/06/12/jemalloc-postmortem/ https://jasone.github.io/2025/06/12/jemalloc-postmortem/

vintermann 7mo ago
"Were I to reengage, the first step would be at least hundreds of hours of refactoring to pay off accrued technical debt." Facebook's coding AIs to the rescue, maybe? I wonder how good all these "agentic" AIs are at dreaded refactoring jobs like these.
- xxs 7mo ago
  Refactor doesn't mean just artificial puff-up jobs, it's very likely internal changes and reorganization (hence 100s of hours). There are not many engineers capable of working on memory allocators, so adding more burden by agentic stuff is unlikely to produce anything of value.
- rvz 7mo ago
  > Facebook's coding AIs to the rescue, maybe? I wonder how good all these "agentic" AIs are at dreaded refactoring jobs like these. No. This is something you shouldn't allow coding agents anywhere near, unless you have expert-level understanding required to maintain the project like the previous authors have done without an AI for years.
  - kenferry 7mo ago
    Hm, I wonder. I've done some work in this sort of area before, though not literally on a malloc. Yes you very much want to be careful, but ultimately it's the tests that give you confidence. Pound the heck out of it in multithreaded contexts and test for consistency.
    - vlovich123 7mo ago
      AI is more than happy to declare the test wrong and “fix it” if you’re not careful. And the cherry on top is that sometimes the test could be wrong or need updating due to changed behavior. So…
    - rvz 7mo ago
      > ...but ultimately it's the tests that give you confidence. Pound the heck out of it in multithreaded contexts and test for consistency. I don't think so. Even on LLM generated code, it is still not enough and you cannot trust it. They can pass the tests and still cause a regression and the code will look seemingly correct, for example in this case study [0]. [0] https://sketch.dev/blog/our-first-outage-from-llm-written-code https://sketch.dev/blog/our-first-outage-from-llm-written-co...

echelon 7mo ago

If you filter the commits to the past five years, four of the top six committers are Meta employees. The other two might be as well, it just doesn't say that on their Github / personal website.