[erlang-questions] Erlang processes and state management design

Thomas Lindgren <>
Wed Oct 24 16:56:46 CEST 2007


--- Alexander Lamb <>
wrote:

> But you seem to not consider solution 2 (process
> dictionnary). Is  
> this because it is not efficient, or at least not
> more efficient than  
> parameters?

I'd recommend not relying on the process dictionary.
Granted, there are cases when it is useful, but you
get all the problems of (process-)global variables
too.

> Also, I read somewhere that the heap for processes
> in Erlang was  
> rather small for historical reasons. If I store data
> in the  
> parameters or in the process dictionnary, will I run
> into some limit?

A process heap is by default small _initially_, but it
will grow dynamically on demand. It's just an
optimization to permit plenty of processes without
running out of memory.

> Alternatively, I suppose the data for ETS structures
> are stored on  
> the node's heap and not in the process heap? Is this
> correct?

As far as I know, yes. However, reading data from ets
copies it into the process heap. (As I understand it,
this is true even for the hybrid runtime system.)

Best,
Thomas


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