Jemalloc 5.4.0

137

ggkfasdfasdf about 5 hours ago 37 commentsRead Article on github.com

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Discussion (37 Comments)Read Original on HackerNews

vocx2tx•about 4 hours ago

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

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

albertgoeswoof•8 minutes ago

I switched to jemalloc on a sidekiq queue and memory dropped from 8gib to under 1gib

There’s a slow memory leak somewhere in my code but with jemalloc it no longer actually matters.

Thanks to jemalloc team for this!

lordnacho•about 2 hours ago

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

jibcage•18 minutes ago

Fun grammatical fact that I only learned after years of speaking French: when borrowing words from other languages, you usually (not always) take the gender of the equivalent word in French, so technically it would be “de la memory” :)

thrance•1 minute ago

[delayed]

sam_lowry_•about 2 hours ago

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 engage in word play on other occasions, so probably not.

tefkah•about 1 hour ago

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

eliaspro•about 1 hour ago

"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/

simonask•about 2 hours ago

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

u8080•40 minutes ago

Memory je Srbia

ksec•about 2 hours ago

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•about 2 hours ago

> Just wish we have a little bit of context

See the comment of vocx2tx

feldrim•about 1 hour ago

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

skavi•about 1 hour ago

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•41 minutes ago

(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•44 minutes ago

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•about 4 hours ago

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

imhoguy•about 2 hours ago

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•about 1 hour ago

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

smartmic•about 1 hour ago

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 …

aktenlage•about 4 hours ago

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

charcircuit•about 1 hour ago

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•about 4 hours ago

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•about 4 hours ago

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•about 3 hours ago

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

stackghost•about 2 hours ago

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•about 1 hour ago

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•about 1 hour ago

>...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•about 2 hours ago

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•about 3 hours ago

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•about 3 hours ago

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•about 2 hours ago

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

HackerThemAll•about 3 hours ago

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.

gjvc•about 1 hour ago

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

kreco•41 minutes ago

> Why is this on the HN front page?

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