[erlang-questions] RE Fwd: FW: Maximising memory compactness

Olivier BOUDEVILLE olivier.boudeville@REDACTED
Fri Apr 4 16:11:29 CEST 2014


> As a matter of fact, the half-word emulator will be deprecated in 
> OTP 17.0, which will be released next week. The reason for that is 
> that there have been very few (if any) users; and thus, the 
> maintenance costs outweigh its value.
> Andreas Schumacher, Erlang/OTP, Ericsson AB

Thanks to all for your pieces of advice; so we will stay away from the 
half-word emulator then (despite its interesting features), and probably 
bet on multiple 32-bit VMs instead.

Jesper: I should have mentioned that we are not using ETS (just many 
processes, each looping over its own state, seen as a mere Erlang term).

Daniel : indeed, in terms of memory, we would lose, for each additional 
node, the base footprint of a blank VM + application-specific modules and 
all; but I think overall we would still gain *a lot* (of course this would 
deserve being verified!); currently processings and data are rather 
well-dispatched, everything is quite fine grain, hence we can keep a 
uniform solution (no ETS node or alike); the goal of an increased in-RAM 
compactness is to be able to reduce the number of nodes, which we believe 
is the biggest showstopper in terms of scaling

Thanks for your answers!

Best regards,


> -----Original Message-----
> From: erlang-questions-bounces@REDACTED [mailto:erlang-questions-
> bounces@REDACTED] On Behalf Of Kostis Sagonas
> Sent: den 4 april 2014 11:39
> To: Erlang
> Subject: Re: [erlang-questions] Maximising memory compactness
> On 04/04/2014 10:33 AM, Olivier BOUDEVILLE wrote:
> > Let's suppose one would like to run a large, distributed (Erlang)
> > application, with many processes, and that ends up, in some cases,
> > being RAM-bound.
>  > ...
> > The half-word emulator would seem the simplest/most elegant solution
> > to do so ....
>  >
> > So, my question: would relying on a set of 32-bit VMs per host,
> > instead of a single 64-bit VM, look like the best option here?
> My opinion is (and has always been) that the half-word emulator 
> seems cute on the surface but deep down is a bad idea (esp. for a 
> language with automatic memory management like Erlang, or if your 
> application has any plans of growing someday).
> So I would really advice against it. In fact, IMO it's better to try
> to forget about its existence for anything other than for small 
> embedded devices or in machines that do not have more than 3GB of 
> Unfortunately, I am very busy to elaborate more on this right now. 
> But even if I had more time, I would probably try to find better 
> things to do than think/talk about the half-word emulator. Leaning 
> back and relax until you forget about it (or simply waiting for the 
> day that it is taken out of the distribution) is preferable IMO.
> Kostis
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