[erlang-questions] inaccurate interval timer

[Jesper Louis Andersen]

On Nov 15, 2012, at 4:12 AM, Mark Geib <mark.geib.44@REDACTED> wrote:

> I am using timer:send_interval(..) to generate recurring messages that drive the sending of UDP packets at a given rate. However, using a network analyzer I am observing that the network datagrams are being sent at a rate greater than the intended rate. Log messages with timestamps indicate the erlang code is sending the datagrams at the proper time. So the question is whether the erlang VM could possibly have a clock that is "tic-ing" at a incorrect frequency, or this an issue with the underlying OS, linux in this case. The interval of the timer is set to 25ms, I am observing times of 23.7-24.5ms. Also, this is only happening on a single machine, testing on four other machines confirms proper rates are being generated.

Since you are only observing the odd behaviour on a single machine, I would expect that machine to be the culprit of the problem more than Erlang. It could be that the machine is running in a configuration which is slightly off. Or perhaps it is virtualized?

Jesper Louis Andersen
  Erlang Solutions Ltd., Copenhagen