Re: [Caml-list] make[1]: warning: Clock skew detected. Your build may be incomplete.

[skaller <skaller@users.sourceforge.net>]

On Wed, 2006-09-06 at 15:36 +0200, Mattias Waldau wrote:
> Hi,
> 
> Got my new laptop with a Intel dual core. I get these funny messages. I 
> use Ocamlmakefile and ocaml under Cygwin on WinXP.
> 
> Any ideas why?
> 
> Anyone else getting these messages?
> 
> make[1]: Warning: File `libraries/ocaml/date_helper.cmo' has 
> modification time 0.0041 s in the future

Regularly? 

This is probably a kernel and/or motherboard fault.

I had this problem with my dual core AMD64, only it wasn't
wrong by 0.0041 s .. it was running almost double speed.

The reason is related to the fact my board supports variable
frequency CPU operation: when the load is low, it drops the
CPU frequency, voltage, and fan speeds to conserve power
and reduce noise. I had to disable this feature entirely.
Both Windows and Linux seemed to suffer. On Linux the 
problem also went away using non-SMP kernel.

Also, my Linux system (and probably Windows) uses network
time server adjustment. Unfortunately, unlike old synchronisers,
these modern ones just reset the clock, without worrying
about screwing up file times (old ones would just speed up
or slow down the clock marginally until the clock was right).

I have no idea if this is your problem, but warn that time
on some motherboard/SMP kernels is potentially bugged.

It is possible the problem is software is using
the CPU clock for timing, instead of the RTC, since RTC
typically have only very coarse resolution.

In that case, the software is using a clock
which isn't regular. Check your bios, and try turning
off variable frequency CPU operation, see if that fixes it?

-- 
John Skaller <skaller at users dot sf dot net>
Felix, successor to C++: http://felix.sf.net