DragonFly bad performance with RIAK benchmark

[Michael Neumann]

On Fri, Aug 14, 2020 at 10:24:00AM +0200, Jávorszky Balázs wrote:
> Hi,
> 
> We are using RIAK as our database, and for various reasons (well, TrueOS 
> has been abandoned...), we need to pick a new OS.

Can you try some gerneral Erlang/Elixir benchmarks first? I doubt it's
really DragonFly or HAMMER2 that slows down that much but rather the
Erlang port that might miss some optimizations on DragonFly. It could be
a missing #ifdef in the Erlang scheduler for instance. I had been
running Elixir and Erlang myself on DragonFly but never did any serious
performance comparisons. One further thing you could try is to run Riak
on DragonFly with different numbers of Erlang scheduler threads (+S)
or turn off SMP just to see if it makes a difference. If you are more
experienced, you could look for #ifdef __FreeBSD__ in the Erlang code 
and see if there is an appropriate #ifdef __DragonFly__ as well, or if
the #else branch falls back to some generic, slow code.

Regards,

  Michael