[erlang-questions] 64-bit erlang

Ulf Wiger (TN/EAB) ulf.wiger@REDACTED
Wed Nov 28 10:02:08 CET 2007

We've had reason to start discussing 64-bit Erlang, and
I thought I'd share some thoughts, hoping that others will
share theirs.

In one application, we're starting to hit the 4 GB ceiling,
and we're discussing ways to address the situation. One
option is to install more RAM, but then we need to either
run multiple nodes on each machine (affects software
complexity), or switch to 64-bit Erlang.

But 64-bit Erlang consumes up to twice as much memory as
32-bit Erlang, so if we switch to more expensive RAM and
install 8 GB, worst case, we'll still have roughly the
same capacity. The cost per GB goes up, which cuts into
the per-unit profit margin.

After this, we'd be able to sail into the sunset on 64-bit
Erlang, installing more and more gigabytes of RAM.  (:
But the entry threshold /is/ a bit high.

Here's an idea to get the discussion going:

How about using 32-bit words inside the process heap, and
"far pointers" to any off-heap data (including other

After all, I doubt that anyone is seriously looking at having
process heaps larger than 4 GB...

Ulf W

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