BEAM process has its own stack and heap for small data binaries(<64bytes) Larger binaries are stored in a shared memory space with a ref-counted pointer(called ProcBin) that lives in a Process's heap. There are many data stacks and heaps in our application, one per process.
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Generational - minor garbage collection. This method reclaims heap memory that is no longer referenced by the process. Idea: most memory is only used for a short period of time. It is highly performant, but looks at recently allocated
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Full-sweep - major garbage collection. This method looks at the entire heap of a process, and reclaims as much memory as possible. Idea: memory must be clean when the heap is close to being full. It is fast in practice, but it can be slow if executing on a process that is actively holding a lot of data
How to collect data manually
- From OTP 20 provide a function to reclaims the memory in a process: :erlang.garbage_collect/1. We can use :erlang.garbage_collect/0 to trigger garbage collection for the process that invoked the function
- Passing the :hibernate_after option for GenServer.start/3 function. The data will be reclaims when the process is idled. Ex: Phoenix Channel use hibernate_after to enter hibernation 15 seconds after processing their last message.
- Returning :hibernate at the end of the GenServer callbacks
def handle_call(:clear, _from, _state) do
{:reply, :ok, [], :hibernate}
end
