"calcru: runtime went backwards" messages

Jeff Dowsley jeff.dowsley at mac.com
Sat Jun 12 00:00:54 UTC 2010

You're not alone.  Noticed the calcru messages after a rebuild in May  
on a Compaq PIII, but assumed it wasn't doing any harm, and that it  
would eventually be fixed.


M 0427565791

jeff.dowsley at mac.com

On 11/06/2010, at 4:03 PM, Jansen Gotis wrote:

> On Fri, Jun 11, 2010 at 7:03 AM, Jilles Tjoelker <jilles at stack.nl>  
> wrote:
>> On Fri, Jun 11, 2010 at 12:35:05AM +0800, Jansen Gotis wrote:
>>> Hi, for the past couple of months since moving to RELENG_8 I've been
>>> receiving "calcru: runtime went backwards" messages on the console.
> <snip>
>> This may well be a manifestation of a brokenness (which should not be
>> unknown) in how FreeBSD stores CPU time utilization. The time is
>> maintained in "CPU ticks" (CPU clock cycles), so if the clock  
>> frequency
>> changes, the values of existing processes will be wrong (a jump when
>> converted to seconds). When calcru detects this, it generates  
>> messages
>> like the above. If this analysis is right, the messages can be  
>> ignored,
>> but indicate that CPU time statistics may be inaccurate.
> You're probably right, the messages can be ignored. I don't see any  
> issues
> other than the messages being printed on the console; I don't  
> experience
> freezing, etc. It just struck me as weird because searching the - 
> current and
> -stable mailing lists does not show anyone else having the issue as  
> recently
> as I have.
> Just some more info to add which I forgot about last time...setting  
> kern.hz to
> 100 did not help.
> Thanks for the reply.
> Best regards,
> Jansen
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