dbg suspend of traced process

Peti Gömöri gomoripeti@REDACTED
Mon Jun 15 15:49:00 CEST 2020

thanks Lukas, nice PR, I'll give it a try, hope it will make it into OTP,

On Mon, Jun 15, 2020 at 10:16 AM Lukas Larsson <lukas@REDACTED> wrote:

> On Fri, Jun 12, 2020 at 11:07 PM Peti Gömöri <gomoripeti@REDACTED> wrote:
>> Hi,
> Hello,
> I noticed that dbg suspends the traced process, when it receives a
>> function-called trace from it.
>> https://github.com/erlang/otp/blob/master/lib/runtime_tools/src/dbg.erl#L875
>> I kind of feel what could have been the original intent behind this, but
>> isn't this something, similar to sender punishment for long message queues,
>> that was more relevant in non-SMP mode, and could be removed?
>> Even so, as it only happens for "trace" messages, and not when timestamp
>> is enabled ("trace_ts"), which sounds like an accidental asymmetry.
>> I am curious what are the details and history behind this selective
>> suspend?
> I don't remember exactly why, but I do believe that you are correct that
> is a mechanism that is no longer useful when running in an SMP system. In
> fact, this pr https://github.com/erlang/otp/pull/2475, which I worked on
> a while ago, removes that backpressure mechanism and instead uses the
> logger_olp module.
> Lukas
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