[erlang-questions] enif_send backpressure

[Daniel Goertzen]

Could the existing implementation of enif_send() do a thread yield when
sending to a congested process?

The first env param will tell you if this is a created thread or process
thread, so either a thread yield or sender punish could be performed.


On Thu, May 25, 2017 at 7:44 AM Roger Lipscombe <roger@REDACTED>
wrote:

> On 25 May 2017 at 13:20, Roger Lipscombe <roger@REDACTED> wrote:
>
>> It's my understanding that if a normal Erlang process does Pid ! Msg, and
>> Pid has a particularly full message queue, then the sending process is
>> penalised (gives up the remainder of its timeslice, e.g.).
>>
>
> I found the relevant code. Search for erts_use_sender_punish in the OTP
> source.
>
> Is there any way to implement something similar for enif_send from a NIF?
>>
>
> Note that enif_send calls erts_queue_message, which *does* return the
> recipient's queue length (afaict). It's just that enif_send discards the
> result. Would a PR which implemented (e.g.) enif_send_return_len -- naming
> is hard, suggestions appreciated -- be considered for OTP 20.x?
>
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