Unified heap (was: Re: R8B PRE-RELEASES)

Per Bergqvist <>
Wed Oct 10 13:29:39 CEST 2001

I am also a believer in the unified heap (or rather any technique that
avoids memory copying)
both by gut feeling and experience.

I have always seen great performance improvements in my code with such
techniques (i.e. vee in
the good old days/dark ages and unified heap) and but for some strange
reason I seem to be
rather lonely with such findings. The majority of the community seem to
get less improvements.

It probably has to do very much with design patterns. I think that the
greatest thing with Erlang is that
the low cost processes allows designs where you don't have to mix
behaviours in processes.
Instead you have many, many small and simple independent but cooperating
The code become much cleaner easier to understand.
(I my opinion this really the core in why it is possible to build such
great systems with Erlang.)

To avoid getting performance boosts with unified heap you probably need
to avoid message
passing and have few complex processes in your application.

I think that nobody can argue unnecessary memory copying is of evil.
(It is a performance killer for every system, it takes time, trash caches

What should be discussed is garbage collection.
The critic of schemes avoiding memory copying always seems to be that a
good gc
will be very very hard if not impossible.
Is that really true ? I am not the man to answer.
It is true that the current gc enables a smooth execution and it is quite
uncommon with
long time system stalls for gc.

Comments anyone ?


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