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Meta’s renewed commitment to jemalloc

engineering.fb.com

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Re: Meta’s renewed commitment to jemalloc

#91

Post by adgjlsfhk1 »

cogman10 wrote: post #69
xxs wrote: post #49

Earlier quoted context omitted.

What do you mean - if Java returns memory to the OS? Which one - Java heap of the malloc/free by the JVM?

Java is pretty greedy with the memory it claims. Especially historically it was pretty hard to get the JVM to release memory back to the OS. To an outsider, that looks like the JVM heap just steadily growing, which is easy to mistake for a memory leak.

This only really ends up being a problem on windows. On systems with proper virtual memory setups, the cost of unused memory is very low (since the the OS can just page it out)

Re: Meta’s renewed commitment to jemalloc

#92

Post by xxs »

yxhuvud wrote: post #84
xxs wrote: post #34

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.

If you changed from glibc to jemalloc and that solved your issues, then you should blame glibc, not the JVM.

Well, indeed - I thought that part was obvious reading it.

Re: Meta’s renewed commitment to jemalloc

#93

Post by flykespice »

tonfa wrote: post #55
flykespice wrote: post #30

Jemalloc also is used by android bionic libc library

Doesn't it depend on vendors/customization? Default is https://llvm.org/docs/ScudoHardenedAllocator.html since Android 11 (2020).

I don't know, that is probably the case I guess?

I was recently debugging an app double-free segfault on my android 13 samsung galaxy A51 phone, and the internal stack trace pointed to jemalloc function calls (je_free).

Re: Meta’s renewed commitment to jemalloc

#94

Post by Dylan16807 »

bmenrigh wrote: post #8

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…

I think some operating system improvements could get people motivated to use huge pages a lot better. In particular make them less fragile on linux and make them not need admin rights on windows. The biggest factor causing problems there is that neither OS can swap a 2MB page. So someone needs to care enough to fix that.

Re: Meta’s renewed commitment to jemalloc

#95

Post by celdon25 »

> Building a software system is a lot like building a skyscraper: The product everyone sees is the top, but the part that keeps it from falling over is the foundation buried in the dirt and the scaffolding hidden from sight.

They should have just called it an ivory tower, as that's what they're building whenever they're not busy destroying democracy with OS Backdoor lobbyism or Cambridge Analytica shenanigans.

Edit: If every thread about any of Elon Musk's companies can contain at least 10 comments talking about Elon's purported crimes against humanity, threads about Zuckerberg's companies can contain at least 1 comment. Without reminders like this, stories like last week's might as well remain non-consequential.

Re: Meta’s renewed commitment to jemalloc

#96

Post by twodave »

jshorty wrote: post #83

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

While it may seem directly related, it's just not. These things are worked on regardless of how cheap or expensive RAM is, because optimizing memory footprint pretty much always leads to fewer machines leased, which is a worthwhile goal even for smaller shops.

Re: Meta’s renewed commitment to jemalloc

#97

Post by alex1138 »

bluGill wrote: post #60
bfgeek wrote: post #11

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").

Facebook had talks already years ago (10+) - nobody was allowed to share real numbers, but several facebook employed where allowed to share that the company has measured savings from optimizations. Reading between the lines, a 0.1% efficiency improvement to some parts of Facebook would save them $100,000 a month (again real numbers were never publicly shared so there is a range - it can't be less than $20,000), and s…

I've heard of some people getting banned from FB to save memory space? Surely that can't be the case but I swear I've seen something like that

Re: Meta’s renewed commitment to jemalloc

#98

Post by refulgentis »

jshorty wrote: post #83

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

There’s been shocks at hyperscaler scale, ex. this got yuge at Google for a couple years before ChatGPT

Re: Meta’s renewed commitment to jemalloc

#99

Post by HackerThemAll »

bluGill wrote: post #60
bfgeek wrote: post #11

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").

Facebook had talks already years ago (10+) - nobody was allowed to share real numbers, but several facebook employed where allowed to share that the company has measured savings from optimizations. Reading between the lines, a 0.1% efficiency improvement to some parts of Facebook would save them $100,000 a month (again real numbers were never publicly shared so there is a range - it can't be less than $20,000), and s…

> LLMs are at most another factor added on

At most... Think 10x rather than 0.1x or 1x.

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