[erlang-questions] erlang:system_monitor in production?

Peti Gömöri <>
Wed Apr 29 19:52:51 CEST 2015


there is a related open pull request https://github.com/erlang/otp/pull/664

On Wed, Apr 29, 2015 at 6:45 PM, Roger Lipscombe <> wrote:
> Hmmm. Could that not be fixed with the new timing stuff in 18? It only
> needs this-scheduler elapsed-time, right?
>
> On 29 April 2015 at 15:50, Roberto Aloi <> wrote:
>> Hi Roger,
>>
>>> Is it OK to have erlang:system_monitor permanently enabled in production?
>>
>>
>> One problem with `erlang:system_monitor/X` combined with an option such as
>> `long_gc`
>> is that, for each GC, the C equivalent of `erlang:now/0` - which has some
>> very well known overhead - is called before and after each GC:
>>
>> https://github.com/erlang/otp/blob/feb45017da36be78d4c5784d758ede619fa7bfd3/erts/emulator/beam/erl_gc.c#L421
>>
>> In other words, keeping long_gc monitoring enabled will add a couple of sync
>> points for each GC.
>>
>> Disclaimer: It was not me discovering this, but a colleague, so not taking
>> any merit or blame for the discovery.
>>
>> Roberto
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