[erlang-questions] Millions of processes?

Nicolas Niclausse <>
Tue Sep 23 17:34:33 CEST 2008

Ulf Wiger (TN/EAB) ecrivait le 23.09.2008 17:14:
> Nicolas Niclausse skrev:
>> Bard Bloom ecrivait le 23.09.2008 15:22:
>>> I've seen in Erlang promotional materials some rather impressive claims
>>> about how cheap Erlang processes are, and how many of them one can
>>> spawn. Which is pretty cool. But, what Erlang programs take advantage of
>>> that kind of power? Are there any examples of programs which use huge
>>> numbers of processes in interesting ways? (I am the local Erlang
>>> fancier. I got challenged on that point, and didn't have a very good
>>> answer.)
>> You can use tsung to simulate millions of users to do load/stress
>> testing.
>> It uses an erlang process for each simulated user.
>> I tried to simulate ~1.3 million users, distributed on ~30 nodes, with
>> one
>> smp beam per node, to see if it works. it does :)
> Yeah, but that's just some 43k processes per node then. (:

Yes, i didn't have enough memory on nodes so i had to use many of them :)
(4GB per node with a 64 bit erlang VM)

> Don't you also run into the problem that practically every
> process in tsung does network IO?

No. But each node had a gigabit ethernet link, and not all users
(processes) were doing network IO simultaneously in the test (because of
"thinktimes" in the scenario ), it was something like 10% of them.
The cumulative bandwitdh was "only" 1Gbit/s


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