See erlang/otp#10113
Once Riak is upgraded to OTP28, there should be a (default) configuration option to run with OTP memory allocators with MADV_DONTNEED not MADV_FREE.
There have been historic issues in Riak with false reporting of memory leaks, as using MADV_FREE may lead to the OS incorrectly reporting memory as being owned by the beam process when in fact it has been released.