[erlang-questions] : Subtle behaviour of Erlang scheduler

Tue May 29 10:22:23 CEST 2007

On Mon, May 28, 2007 at 10:52:58PM +0200, Ulf Wiger (TN/EAB) wrote:
> Corrado Santoro wrote:
> > 
> > But this does not mean that, in my opinion, the Erlang 
> > priority system has a serious flaw and should be rethought. 
> > Probably, in a telecommunication system, priorities could not 
> > be so important, but if you use Erlang in real-time embedded 
> > environment (and it's argued that Erlang is for 
> > soft-real-time systems),
> Indeed, telecommunication systems are soft-real-time,
> which means that it is sufficient to meet deadlines 
> in a high percentage of the cases, but missing a 
> deadline is not considered a fatal error.
> Erlang shines in this regard, IMO, but in my experience,
> process priorities don't do much to help in this type
> of system. Thus the recommendation to use 'normal'
> priority in the vast majority of cases.

Well, guys, I thought Erlang was really going to be used in many
different application fields, from telecommunication platforms to web
apps, from massively concurrent systems to distributed high
performance applications.

I also dreamed about Erlang as a real, affordable, safe and robust
alternative to many ugly and still widely-used languages and
platforms, such as C#/.net and Java, or at least I understood so,
attending the last two Erlang User Conferences in 2005 and 2006.
I also started to talk about erlang at university courses.....

But the last two mails, which suddenly close the Pandora Vase we
opened looking a little deep inside the process scheduler, simply
explain that Erlang developers (or at least Ericsson OTP group), has
little or no interest on having a real robust, affordable,
distributed, secure and real-time platform.

After we discovered a big bug in the scheduler, and reported it to the
community, the only answer we got was: we don't use that scheduler
code in OTP, this bug does not heavily affect OTP, processes in
telecom apps usually use normal priority and since telecom apps are
our main business and represent 90% of actual Erlang code, it does not
matter for us. 

Well, maybe it does not matter for telecom apps, maybe it does not
matter for 90% of Erlang code, maybe it is a so rarely used feature,

The discussion is closed, also for me. But I would rather prefer to
avoid this kind of mails......



[ Enzo Nicosia aka KatolaZ --- GLUG Catania -- Freaknet Medialab ]
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