[erlang-questions] Erlang vs Clojure

Alex Arnon <>
Wed Nov 28 10:31:03 CET 2007


I remember seeing some posts about inroads being made with regard to
realtime performance on JVMs lately, on Lambda the Ultimate.
On the other hand, listening to Software Engineering Radio
(this<http://www.se-radio.net/podcast/2007-10/episode-73-real-time-systems-bruce-powel-douglass>one
I think), the expert being interviewed said that Java is practically
nonexistent in the realtime space. So... grains of salt with everything, as
usual... :)


On Nov 28, 2007 4:23 AM, G Bulmer <> wrote:

>
> A small point about JVM concurrency performance.
> I had the pleasure of talking to James Gosling one to one, for a
> couple of hours, about three years ago, in Bangalore.
>
> He was presenting a talk about his current and on-going work on Java.
> He said he spent much of his time on strategic Java projects.
> He very excited about a research JVM which was being built and tested
> for use in hard realtime, the project he talked about as specifically
> for process control in a power plant.
>
> Anyway, in his initial presentation (after which we chatted) he
> showed stats from the research JVM that indicated good support for
> many thousands of threads (I accept, still well behind the Erlang VM,
> but I'd need more detail to judge how far behind) with interrupt
> response times with a jitter of less than 4 micro-seconds  (I am sure
> this was at least response to timer events, and may have been to
> other interrupt sources).
>
> I am certain I asked about garbage collection, and he said that the 4
> micro-seconds was not an overall average, but was 'realtime', and it
> included garbage collection.
>
> I don't recall many more details other than the company involved in
> the process control project (who I feel I should not disclose as he
> was tired, jet lagged, home sick for his kids, and maybe a little
> tipsy).
>
> Anyway, I don't assume that the normally resource-expensive JVM
> approach to threads is the only practical solution. There is likely
> significant investment in fixing some of those Java problems.
>
> GB
>
> PS - I apologise that I haven't followed it up. I remember at the
> time feeling I should not expect to see anything for a year or more.
> I may try digging some time next week (when I return from my lovely
> Thai holiday, the weather is beautiful here, much warmer than
> Stockholm EUC, and booze and food are cheaper too :-)
>
>
> > Date: Mon, 26 Nov 2007 09:43:18 +0000
> > From: Charles Forsyth <>
> > Subject: Re: [erlang-questions] Erlang vs Clojure
> >> The thought of running on the JVM makes me feel both sick and
> >> bloated...but strangely I am warming up to the idea.
> >>
> >
> >
> >> The ErlangVM enables distributed concurrency, Closure on the JVM is
> >> optimizing for local concurrency.
> >>
> >
> >
> >> Granted that I am not building fault tolerant telecom switches,
> >> but in
> >> my case, massive local concurrency might be all that I need.  With
> >>
> >
> > if you expect to get high-performance concurrency from a JVM
> > i expect you to be disappointed.  the Erlang implementation
> > guarantees cheap processes everywhere it exists.  by contrast,
> > you get whatever your particular JVM gives you, which might not
> > be much, and it will vary from platform to platform.
> > if it works for you, though ...
> > i'd be particularly interested if you find JVMs that
> > offer ``massive local concurrency''.
> >
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