[erlang-questions] erlang time in vmware

Richard Andrews <>
Sat Nov 17 00:26:05 CET 2007


> My Erlang VM however, ended up ~270 seconds into the future after 
> running for about a week. The system time as reported by 'date' showed 
> correct time. Can someone explain this, and hopefully also tell me how 
> to avoid it in the future?

>From my observations of erlang under Linux via strace I see that it makes
extensive use of clock_gettime( CLOCK_MONOTONIC ). CLOCK_MONOTONIC combined
with vmware modifying kernel clock ticks might lead to this effect. If vmware
inserts additional timing ticks to try and acount for time periods in which the
guest kernel is not running, then erlang might see the time as in the future if
it measures wall time as (StartTime + Ticks).

Just guessing though.

I don't see an obvious way to avoid it, except to use a vmware supported
OS-specific mechanism to get wall-clock time.



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