[erlang-bugs] http://www.erlang.org/faq/academic.html - section 10.23 with respect to shared heap needs correction?

Björn-Egil Dahlberg <>
Mon Dec 10 02:04:39 CET 2012

2012/12/10 Matthias Lang <>

> On Thursday, November 29, Joseph Wayne Norton wrote:
> > I noticed the last statement of section 10.23 with respect to shared
> > heap.  It seems this feature is no longer supported or is
> > undocumented?  If it is still present, could you point me to the
> > appropriate documentation?
> The shared/hybrid heaps are gone as of at least ERTS 5.9.2, according
> to the release notes (OTP-10105):
>   http://www.erlang.org/doc/apps/erts/notes.html
> Thanks for pointing out that the FAQ still talks about them. For now,
> I've fixed it by removing the last paragraph from the FAQ entry. It'll
> automagically propagate to erlang.org, probably within an hour.
> To someone who knows: is the description of GC in that section still
> correct? Specifically, does GC of one process still freeze all other
> processes, even when running SMP?

It will "freeze" the scheduler thread running that particular process. It
will also "freeze" any other process in the run-queue coupled to that
particular thread.
This is not any big problem unless the heaps of the process are unusually

Any other threads and processes are unaffected.

// Björn-Egil

> If your (Joseph's) main interest in this is trying out the shared and
> hybrid heap, then the only way I know of is to go back to the Erlang
> versions which supported it. A good start is probably ERTS 5.4.9
> (somewhere in the R10B-x series). Here's one I had lying around:
>   otp_src_R10B-10 >bin/erl -hybrid
>   Erlang (BEAM) emulator version 5.4.13 [64-bit] [source] [hybrid heap]
> A bit of googling gives some background to the shared/hybrid
> emulator's fate:
>   http://erlang.org/pipermail/erlang-questions/2009-September/046428.html
> http://www.trapexit.org/forum/viewtopic.php?t=2956&sid=d3c1c76aa5e04465902c071efa7195ba
> Matt
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