Hacker News

Jemalloc 5.4.0

120 points by gkfasdfasdf ago | 34 comments

vocx2tx |next [-]

For some context on why this release is notable: Jemalloc Postmortem [0]

[0] https://news.ycombinator.com/item?id=44264958

lordnacho |next |previous [-]

I always wondered, is it French? "Je m'alloc du memory"

sam_lowry_ |root |parent |next [-]

Rather a tradition to call a malloc by the initials of the implementer: Jason Evans malloc (jemalloc), Poul-Henning Kamp malloc (phkmalloc), Doug Lea (dlmalloc).

P.S. I also wondered whether systemd had any cultural reference to Système D aka Système Débrouillard, but Pottering does not seem to be someone engaging in word play, so probably not.

tefkah |root |parent [-]

damn i always thought it was a french thing, this is blowing my mind

eliaspro |root |parent [-]

"Yes, it is written systemd, not system D or System D, or even SystemD. And it isn't system d either. Why? Because it's a system daemon, and under Unix/Linux those are in lower case, and get suffixed with a lower case d."

Source: https://brand.systemd.io/

u8080 |root |parent |next |previous [-]

Memory je Srbia

simonask |root |parent |previous [-]

Thanks, now my brain will forever read it like that. I'm not even a little bit French.

ksec |next |previous [-]

Ok. Why both the homepage and its Github repo doesn't make a single mention of Jason Evans? I know he stepped down but surely it is at least worst mentioning it?

Is Meta still using it and developing it? If not who are the driving force behind it now? I just checked there wasn't a release since 2022 and then we have this now. Something changed?

Just wish we have a little bit of context. But it is also great it is continue being maintained. It makes a huge difference for Ruby on Rails Apps.

aktenlage |root |parent |next [-]

> Just wish we have a little bit of context

See the comment of vocx2tx

feldrim |root |parent |previous [-]

It's only mentioned in history: https://github.com/jemalloc/jemalloc/wiki/Background#history

skavi |next |previous [-]

does anyone familiar with the art have thoughts on why only tcmalloc switched from thread caches to cpu caches? would it make linux behavior diverge too much from other platforms?

rwmj |root |parent |next [-]

(Not an expert but ...) unless you pin threads to cores, which is not the default and somewhat awkward in Linux for user applications, having a per-thread cache doesn't really make sense as your thread could be moved to another core and then your cache will no longer be local to the physical cache.

enduku |root |parent |previous [-]

I think tcmalloc gains on thread churn and oversubscription by going the cpu-cache route on Linux. on other platforms, I am not so sure but that can be offset by say a treiber-stack like setup for cross-thread frees/teardowns. So lesser code for Linux for similar fastpath design I guess.

ZenoArrow |previous [-]

Why is this on the HN front page? Is there something particularly noteworthy about this release?

imhoguy |root |parent |next [-]

I upvoted it because I benefit from jemalloc in my stack (RoR) and I am tired of AI taking over HN front page. Let the hacker spirit be back!

adityapatadia |root |parent |next [-]

Upvoted for the same reason. We would not be able to run our workloads without Jemalloc. Kudos to this awesome piece of software.

smartmic |root |parent |previous [-]

You are not alone - my first thought was 'oh, HN is trying to bring back the disappointed hackers'. All this AI hype over every little model update fart is so exhausting and boring …

kreco |root |parent |next |previous [-]

> Why is this on the HN front page?

This question was not necessary. You know the answer, because people upvoted this.

aktenlage |root |parent |next |previous [-]

They resumed development on jemalloc only recently, after years of no releases.

charcircuit |root |parent [-]

Development was never stopped for jemalloc. This is a common misconception. There just were not releases being tagged and packaged against the ongoing development.

defrost |root |parent |next |previous [-]

The noted resumption and likely a small amount of halo effect from the Comparison of Malloc() Algorithms thread two / three days ago.

- https://news.ycombinator.com/item?id=49715318

ck45 |root |parent |next |previous [-]

I just checked whether it's the first release after Jason Evans stepped down as maintainer, but it isn't. That was the previous release, 5.3.1

baq |root |parent |next |previous [-]

jemalloc is something you should be aware of if you do software for a living

stackghost |root |parent |next [-]

In the Before Times, the vast majority of software was written in garbage collected language where a working knowledge of the relative merits of C memory allocators is not useful or particularly relevant.

Why would the scads of people writing JavaScript, Java, python, go, rails, etc need to be aware of jemalloc?

nh2 |root |parent |next [-]

Memory allocation behaviour has visible impact also for users of managed languages, and the behaviour of software for end users.

In our Python program, a bit of numpy processing of large pictures led to 100 GB not being returned to the OS by glibc's default allocator and the machine running out of memory shortly after. With jemalloc's reliable memory return settings, those problems disappear.

xxs |root |parent |next |previous [-]

>...the vast majority of software was written in garbage collected language

and even then recently it costed (us) quite a few months to blame JVM and later the default glibc memory allocator for running out native (java heap memory) - had to exclude all possible native libs, direct buffers, sockets, thread stacks and so on. Changing the malloc to jemalloc solved the issue, even though initially it was done for its debugging capabilities.

It's just a great memory allocator.

iam-da-author |root |parent |previous [-]

TL;DR: Because the runtime of most GC:d languages uses malloc for its internal data structures.

I work for the runtime team of JPG @ Oracle. We use malloc in Hotspot, quite a lot actually! Providing your JVM with a good malloc can improve the performance of the runtime, both in terms of CPU and memory, by quite a bit.

I don't think you need the details, but it's good to be aware that some mallocs are better than others, and there are multiple of them. Being aware of jemalloc is a good way of being aware of the facts I just mentioned :-).

rfgplk |root |parent |previous [-]

Why? Writing a memory allocator is quite simple, and I'd argue that _everyone_ should write one from scratch for any kind of high performance application. It's also trivial to outperform general purpose allocators that have to satisfy countless constraints. I've written numerous special purpose mallocs that are a) both provably (formally) safer than the standard armada and b) significantly faster (>10x throughput).

groomlake |root |parent |next [-]

Your experience writing memory allocators is irrelevant. The point is that jemalloc is widely used and that’s why it makes sense to be aware of it.

stackghost |root |parent |next |previous [-]

Writing an allocator is simple, you’re correct, but writing an allocator that doesn’t suck is not simple.

HackerThemAll |root |parent |previous [-]

I'd happily see performance, latency and stability of your allocators in massively multithreaded, long-living programs with workloads where hundreds or thousands of parallel threads continuously create and destroy short-lived small and medium objects.

Writing allocators for domain-specific access patterns is easy. Writing a general-purpose high performing, stable allocator with bounded P99 latency is hard.

Give your friend, Dunning–Kruger, some better pills to keep him from speaking through you.

Pannoniae |root |parent |next [-]

You're correct, but his point is that you don't need to solve the generic problem. Solving the generic problem is very hard. Grug doesn't like solving hard problem. What does grug do? Solve five easy problems. Make an arena for the short-lived objects, reuse the objects, use generic multithreaded malloc for the rest. Grug happy.

matheusmoreira |root |parent |previous [-]

Not everything needs to be general purpose. Allocation can be as easy as bumping a pointer, and it's hard to beat that.

gjvc |root |parent |previous [-]

because people like you are too busy whining about it to put up something more interesting