negative runtime etc., the story continues

Yar Tikhiy yar at
Thu Dec 21 04:33:46 PST 2006

On Tue, Dec 19, 2006 at 11:49:43PM +0100, V??clav Haisman wrote:
> Hi,
> I wrote about how FreeBSD 6.1 RC1, with latest RELENG_6 kernel, prints loads
> of "calcru: runtime went backwards..." and "calcru: negative runtime..."
> messages when the FreeBSD runs as virtual server under Microsoft Virtual
> Server 2006 R2. When I wrote this I was compiling and installing lots of
> packages, setting up the OS. Now that it is idle I have noticed one quite bad
> thing. Any process that sleeps on timer or sleep() call will wake up much
> later than it should. For example, when I start top there should be two
> seconds delay between updates of the screen. It takes up to 20 seconds! But
> when there is compilation running or something else CPU intensive, the timer
> seems to work fine.
> I even tried setting different kern.timecounter.hardware (TSC, ACPI-safe,
> i8254) and kern.hz (to lower than the default 1000) but that did not help a bit.
> Is there anything I can do to get rid of the calcru messages apart from
> reinstalling to real hardware?

Last time I was trying to run FreeBSD as a guest OS in MS VS, I
found that TSC would work the best, but only if I made sure that
the TSC frequency was correct.  For some weird reason, the frequency
initially detected by the kernel was totally bogus and changing
from one boot to another, so I just estimated it from cpu-z output
in the host OS, and it fairly worked.  I still couldn't get rid of
the annoying warnings, especially when under load.


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