[erlang-questions] How to tune erlang memory allocator to use 25 GB of ram and stop munmaping it?
Tue Aug 20 12:43:12 CEST 2013
I'm also interested in reducing the OS allocation and free's but for a
different use case:
In small embedded systems with no virtual memory (running on RTEMS
e.g.) there are several problems with malloc/free:
1. its very slow.
2. the system heap fragments. There is no VM to help.
My favorite behaviour would be for Erlang to either grab all memory
available or at least a fixed amount on startup and hold on to it
forever. Hopefully without fragmenting it too much (I know in case of
binary heaps that this isn't possible which is a bit disturbing to me).
Can this be achieved by the current ERTS with some parameter settings?
Which direction should I look if I want to add behaviour like this?
BTW: next best thing is to malloc/free allways same size tiles this
would avoid outer fragmentation and could be sped up relatively easily.
On 2013-08-15 08:05:01 +0000, Lukas Larsson said:
> Did increasing the max mseg_alloc sbc limit help?
> After thinking a bit more on this issue, I think that my original
> hypothesis was correct. You are allocating way more sbc than you want
> to. Moving more of you allocations into mbcs should drastically
> decrease the number of mmaps needed and also instead of placing one
> binary within one mmap area, it will place many binaries within a
> larger mmaped area.
> Do you have any idea of the average sizes of the binaries that you are
> allocating? If you do I would try to set the sbct to be high enough
> that maybe 80% of all binaries fit below it. At the same time you
> should probably also adjust the smbcs and lmbcs to a higher value,
> maybe something like smbcs = 0.5*sbct lmbcs = 10*sbct. If you know that
> you will be using a lot of binaries you could also set smbcs to be
> higher to start with, or decrease the growth stages (mbcgs) so that you
> faster get to the lmbcs. You will have to play around with sbct, smbcs,
> lmbcs and mbcgs and measure performance and memory usage to see what is
> the best fit for you.
> When doing this you can remove the mmsbc config again as you will
> (hopefully) be using very few sbcs.
> On Wed, Aug 14, 2013 at 4:57 PM, Max Lapshin <max.lapshin@REDACTED> wrote:
> Oh, thank you, will try it.
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