[erlang-questions] Early Out of Memory

Patrik Nyblom <>
Fri Mar 1 15:41:38 CET 2013


Hi!

Halfword is limited to 4GB of *total* heap space. In the same way as for 
32bit VM, memory runs out for heaps. ETS tables can be as large as the 
virtual memory, the terms there are stored in mysterious ways :)

/Patrik
On 03/01/2013 02:03 PM, Vance Shipley wrote:
> On Fri, Mar 01, 2013 at 10:33:35AM +0100, Patrik Nyblom wrote:
> }  Looks like you're running a 32 bit VM, in which case you have at a
> }  absolute maximum 4GB of memory. A heap allocation of 1.3 GB means
> }  an old version of the heap of possibly the same size (copying GC) +
> }  old heap generations and so on. A heap also needs to have
> }  continuous virtual memory, so the chance of having a single process
> }  with this much heap running on a 32bit VM is slim at best. If you
> }  have a lot of physical memory in the machine, run a 64bit OS and a
> }  64bit Erlang VM.
>
> Patrik,
>
> Fair enough, I didn't realize that I had forgotten to build R16B as
> 64 bit on my MacBook Pro.  When I did the test happily used up all
> 16GB of physical memory and 10GB of swap before I killed it.
>
> But can you explain this one?:
>
>     Erlang R16B (erts-5.10.1) [source] [64-bit halfword] [smp:8:8] [async-threads:10] [kernel-poll:false]
>     
>     Eshell V5.10.1  (abort with ^G)
>     1> F = fun(F, Acc) -> F(F, [lists:seq(1,1000) | Acc]) end.
>     #Fun<erl_eval.12.17052888>
>     2> F(F, []).
>     
>     Crash dump was written to: erl_crash.dump
>     eheap_alloc: Cannot allocate 790960704 bytes of memory (of type "old_heap").
>     Aborted (core dumped)
>
> Above I am running an R16B 64-bit halfword emulator on a server with 6GB
> of physical memory.
>
> What are the system limits with the halfword emulator?  I assume that I
> can't have a binary over 4GB.  Can I have an ets table bigger than 4GB?
>




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