[erlang-questions] Frequency of module reloading and the constant pool

Edmond Begumisa <>
Sat Sep 16 23:57:36 CEST 2017

On Sun, 17 Sep 2017 03:39:50 +1000, Edmond Begumisa  
<> wrote:

> Hello all,
> (Not new here--just haven't posted in a while!)
> I'm using merl to dynamically generate and regenerate modules at runtime  
> that make use of the ERTS constant pool in order to efficiently avail  
> data to all processes. I'm aware that this technique is known amongst  
> more experienced Erlangers for situations where the data is updated  
> infrequently (e.g. sharing global configuration parameters).
> The question I'm investigating is how frequent is "infrequent" w.r.t  
> reloading of modules[1]? I'm not entirely sure about the costs involved  
> when (re)loading a module so I've got no idea where to start in order to  
> measure the impact on the emulator. Could anybody with sufficient  
> knowledge of emulator internals point me in the right direction?

To clarify: When measuring whether or not I'm hot-code swapping too  
frequently, what are the negative signs to look for? What does the  
emulator actually do when swapping out code w.r.t potentially  
disruptive/costly operations like locking, GC, etc which could negatively  
impact scheduling, memory and responsiveness of the system?

I'm trying to figure out when the best time to reload a dynamically  
generated module/group of modules is and how frequently I should allow  
reloading to occur.

- Edmond -

> Thanks in advance.
> - Edmond -
> [1] The more exotic use-cases for use/abuse of the constant pool and  
> module reloading I'm looking into are to do with caching and incremental  
> computation.

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