[erlang-questions] how are erlang process lightweight?

Ulf Wiger (TN/EAB) <>
Tue Oct 3 12:23:00 CEST 2006

Check out the recent thread at Lambda the Ultimate:

"What Makes Erlang Processess Tick?"


Ulf W 

> -----Original Message-----
> From:  
> [mailto:] On Behalf Of Ben Dougall
> Sent: den 3 oktober 2006 11:31
> To: 
> Subject: [erlang-questions] how are erlang process lightweight?
> Hello,
> I'm trying to find out how Erlang processes work / what 
> they're made of. I know they don't share their memory with 
> each other (have their own heaps), in order to communicate do 
> so by message passing that are serialised data. They run one 
> after another, per cpu/core. The schedular decides which 
> process should get to go next. They stop processing when they 
> come to a point where they're waiting for a message or after 
> they've been processing for a certain amount of time. 
> All this is handled by the language/runtime system and 
> happens within user space.
> Each process is very lightweight. I'm struggling to find out 
> how they're lightweight. They're stackless? Is that correct? 
> On the stack, with things that use them, local variables are 
> stored. What happens to a process's local variables when it's 
> switched out of control (due to coming to a point where it's 
> waiting for a message or reached its time limit)? Each 
> process must have local variables don't they? So what happens 
> to them? Where do they get stored? If you have a set of local 
> variables per process then how is each process considered so 
> lightweight? And if you don't have a set of local variables 
> per process then how can they operate reasonably -- local 
> variables persisting seem essential? A set of local variables 
> must get stored per process and if you have hundreds of 
> thousands of processes that's not so lightweight is it?
> Also how do processes correspond to functions? Is it just one 
> function per process? Processes and functions are very much 
> tied up with each other; one to one?
> Any info or pointers to things that contain info on this 
> would be much appreciated.
> Thanks, Ben.
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