[erlang-questions] Fwd: Maximising memory compactness

[Andreas Schumacher]

That is correct; right now, there are no plans for x32 ABI support.

Andreas

---------- Forwarded message ----------
From: Andreas Schumacher <andreas.schumacher@REDACTED>
Date: Sat, Apr 5, 2014 at 3:01 PM
Subject: [erlang-questions] Maximising memory compactness
To: "andreasschu@REDACTED" <andreasschu@REDACTED>




 *From: *Tuncer Ayaz <tuncer.ayaz@REDACTED>
 *Subject: * *Re: [erlang-questions] Maximising memory compactness*
 *Date: *4 Apr 2014 20:09:58 GMT+2
 *To: *Andreas Schumacher <andreas@REDACTED>
 *Cc: *"erlang-questions@REDACTED" <erlang-questions@REDACTED>

On Fri, Apr 4, 2014 at 5:26 PM, Andreas Schumacher wrote:

Honestly, we did not measure the number of users, but we made a
rough guess based on the questions, comments, and/or bug reports we
got for the half-word emulator.


I'm not arguing for or against halfword-emu, as I'm not the designated
maintainer, but it just works and most likely does for everyone else
who has it enabled. I never had a bug caused by it, and on some
machines it's the reason I can use Dialyzer with an amd64 beam.smp.

If my professional experience with users of code I was responsible for
is any indication, then it's very safe to assume that users only
report bugs. I've learned that users won't even report back if a
hotfix works. Hence, you can't use non-existence of bug reports or
comments as an indication of how widely/successfully something is used.
Some code has vocal users (gamers), most doesn't.


As you didn't answer the x32 ABI question, I take that to mean there's
no plan for that. Correct?

-----Original Message-----
From: Tuncer Ayaz [mailto:tuncer.ayaz@REDACTED <tuncer.ayaz@REDACTED>]
Sent: den 4 april 2014 14:25
To: Andreas Schumacher
Cc: erlang-questions@REDACTED; Olivier BOUDEVILLE
Subject: Re: [erlang-questions] Fwd: FW: Maximising memory compactness

On Fri, Apr 4, 2014 at 1:33 PM, Andreas Schumacher wrote:

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.


FWIW, I use it. But more importantly, how did you measure the number
of users? For comparison, JVM's compressed oops has been default
enabled for a long time, but to be precise it's not _exactly_ the
same thing.

http://docs.oracle.com/javase/7/docs/technotes/guides/vm/performance-enhancements-7.html
"Compressed oops is supported and enabled by default in Java SE 6u23
and later. In Java SE 7, use of compressed oops is the default for
64-bit JVM processes when -Xmx isn't specified and for values of
-Xmx less than 32 gigabytes."

https://wikis.oracle.com/display/HotSpotInternals/CompressedOops

That said, what about implementing x32 ABI support as an
alternative? As far as I can tell this would have to be explicitly
implemented in HiPE too.

-----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
memory.

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.
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