Meta’s renewed commitment to jemalloc

thatoneengineer

First impressions: LOL, the blunt commentary in the HN thread title compared to the PR-speak of the fb.com post. Second thoughts: Actually the fb.com post is more transparent than I'd have predicted. Not bad at all. Of course it helps that they're delivering good news!

oncallthrow

And the Oscar for most mealy-mouthed post of the year goes to…

fermentation

Seems like they’d want to wait to commit until after the layoffs, right?

bmenrigh

I recently started using Microsoft's mimalloc (via an LD_PRELOAD) to better use huge (1 GB) pages in a memory intensive program. The performance gains are significant (around 20%). It feels rather strange using an open source MS library for performance on my Linux system. There needs to be more competition in the malloc space. Between various huge page sizes and transparent huge pages, there are a lot of gains to be had over what you get from a default GNU libc.

dang

Related. Others? Jemalloc Postmortem - https://news.ycombinator.com/item?id=44264958 - June 2025 (233 comments) Jemalloc Repositories Are Archived - https://news.ycombinator.com/item?id=44161128 - June 2025 (7 comments)

markstos

How is the original author making out in the new arrangement?

bfgeek

One has to wonder if this due to the global memory shortage. ("Oh - changing our memory allocator to be more efficient will yield $XXM dollar savings over the next year").

charcircuit

Meta never abandoned jemalloc. https://github.com/facebook/jemalloc remained public the entire time. It's my understanding that Jason Evans, the creator of jemalloc, had ownership over the jemalloc/jemalloc repo which is why that one stopped being updated after he left.

nubinetwork

Someone should tell Bryan Cantrill, he'd probably be ecstatic...

RegnisGnaw

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

flykespice

Jemalloc also is used by android bionic libc library

xxs

Few months back, some of the services switched to jemalloc for the Java VM. It took months (of memory dumps and tracing sys-calls) to blame the JVM, itself, for getting killed by the oom_killer. Initially the idea was diagnostics, instead the the problem disappeared on its own.

pram

I used jemalloc recently for ComfyUI/Wan and it’s literally magic. I’m surprised it doesn’t come that way by default.

starkparker

(wrong thread)

jjuliano

I remember I was a senior lead softeng of a worldbank funded startup project, and have deployed Ruby with jemalloc in prod. There's a huge noticeable speed and memory efficiency. It did saved us a lot of AWS costs, compare to just using normal Ruby. This was 8 years ago, why haven't projects adopt it yet as de facto.

lobf

>We are committed to continuing to develop jemalloc development From the Department of Redundancy Department.

adsharma

> We plan to deliver improvements to [..] purging mechanisms During my time at Facebook, I maintained a bunch of kernel patches to improve jemalloc purging mechanisms. It wasn't popular in the kernel or the security community, but it was more efficient on benchmarks for sure. Many programs run multiple threads, allocate in one and free in the other. Jemalloc's primary mechanism used to be: madvise the page back to the kernel and then have it allocate it in another thread's pool. One problem: this involves zero'ing memory, which has an impact on cache locality and over all app performance. It's completely unnecessary if the page is being recirculated within the same security domain. The problem was getting everyone to agree on what that security domain is, even if the mechanism was opt-in. https://marc.info/?l=linux-kernel&m=132691299630179&w=2

joelsiks

Opening up strong with a gigantic merge of the stuff they've been working on in their own fork: https://github.com/jemalloc/jemalloc/pull/2863

rishabhjajoriya

Large engineering orgs often underestimate how much CI pipelines amplify performance issues. Even small inefficiencies multiply when builds run hundreds of times a day.

jshorty

Surprised not to see any mention of the global memory supply shock. Would love to learn more about how that economic is shifting software priorities toward memory allocation for the first time in my (relatively young) career