Booting 5000 Erlangs on Ampere One 192-core
21 comments
·August 10, 2025Animats
bravesoul2
Thanks for the rabbit hole!
lifeisstillgood
So this is something like a 5000 USD machine (https://www.jeffgeerling.com/blog/2024/ampereone-cores-are-n...) And is designed as a cloud provider or telco edge machine (hence the erlang consultancy)
But if you are looking at a hosted erlang VM for a capex of one dollar then these folks are onto something
Cores really are the only way to escape the broken moores law - and this does look like a real step in the important direction. Less LLMs more tiny cores
ethan_smith
The article is about 5000 Erlang nodes (BEAM VMs), not processes - a single BEAM instance can efficiently handle millions of lightweight processes, making this even more impressive from a density perspective.
alberth
While not this exact server, from Hetzner, you can get an 80-core Ampere for just ~$200 per month.
(And that also includes hosting, egress, power, etc).
bravesoul2
Is that cheaper? 7200 over 3 years. Obviously more convenient though and less capex.
znpy
> Product currently not available
in practice you can't though
sargun
I really like the manycores approach, but we haven’t seen it come to fruition — at least not on general purpose machines. I think a machine that exposes each subset of cores as a NUMA node and doesn’t try to flatten memory across the entire set of cores might be a much more workable approach. Otherwise the interconnect becomes the scaling limit quickly (all cores being able to access all memory at speed).
Erlang, at least the programming model, lends itself well to this, where each process has a local heap. If that can stay resident to a subsection of the CPU, that might lend itself better to a reasonably priced many core architecture.
to11mtm
> Erlang, at least the programming model, lends itself well to this, where each process has a local heap. If that can stay resident to a subsection of the CPU, that might lend itself better to a reasonably priced many core architecture.
I tend to agree.
Where it gets -really- interesting to think about, are concepts like 'core parking' actors of a given type on specific cores; e.x. 'somebusinessprocess' actor code all happens on a specific fixed set of cores and 'account' actors run on a different fixed set of cores, versus having all the cores going back and forth between both.
Could theoretically get a benefit due to instruction cache being very consistent per core, giving benefits due to the mechanical sympathy (I think Disruptors also take advantage of this).
On the other hand, it may not be as big a benefit, in the sense that cross process writes are cross core writes and those tend to lead to their own issues...
fun to think about.
toast0
> think a machine that exposes each subset of cores as a NUMA node and doesn’t try to flatten memory across the entire set of cores might be a much more workable approach. Otherwise the interconnect becomes the scaling limit quickly (all cores being able to access all memory at speed).
Epyc has a mode where it does 4 numa nodes per socket, IIRC. It seems like that should be good if your software is NUMA aware or NUMA friendly.
But most of the desktop class hardware has all the cores sharing a single memory controller anyway, so if you had separate NUMA nodes, it wouldn't reflect reality.
Reducing cross core communication (NUMA or not) is the key to getting high performance parallelism. Erlang helps because any cross process communication is explicit, so there's no hidden communication as can sometimes happen in languages with shared memory between threads. (Yes, ets is shared, but it's also explicit communication in my book)
zozbot234
> Erlang, at least the programming model, lends itself well to this, where each process has a local heap.
That loosely describes plenty of multithreaded workloads, perhaps even most of them. A thread that doesn't keep its memory writes "local" to itself as much as possible will run into heavy contention with other threads and performance will suffer a lot. It's usual to try and write multithreaded workloads in a way that tries to minimize the chance of contention, even though this may not involve a literal "one local heap per core".
leoc
Who knows what will really happen, but there have been rumours of significant core-count bumps in Ryzen 6, which would edge the mainstream significantly closer to manycore.
felixgallo
Paraphrasing the late great Joe Armstrong, the great thing about Erlang as opposed to just about any other language is that every year the same program gets twice as fast as last year.
Manycores hasn't succeeded because frankly the programming model of essentially every other language is stuck in 1950. I, the program, am the entire and sole thing running on this computer, and must manually manage resources to match its capabilities. Hence async/await, mutable memory, race checkers, function coloring, all that nonsense. If half the effort spent straining to get the ghost PDP-11 ruling all the programming languages had been spent on cleaning up the (several) warts in the actor model and its few implementations, we'd all be driving Waymos on Jupiter by now.
hinkley
Azul did something like this back in the ‘10s for Java. But it’s one of those products for when you’ve put all you eggs in one basket and you need the biggest basket money can buy. Sort of like early battery backed storage. T was only fit for WAL writing on mission critical databases because one cost more than a car.
elteto
“ Underjord is an artisanal consultancy …”
kirito1337
Wow man.
"5000 Erlangs" - oh, they meant 5000 instances of some Erlang interpreter. Not Erlang as a unit of measure.[1] One voice call for one hour is one Erlang.
[1] https://en.wikipedia.org/wiki/Erlang_(unit)