[CentOS-virt] Status of kernel divider option in 2.6.9-78.0.1

Wed Sep 17 18:23:17 UTC 2008
Jeff <jlar310 at gmail.com>

Under 4.6, we recompiled the kernel with HZ=100 for improved
time-keeping in VMware guests. I've read about the backporting of the
divider patch into RHEL/CentOS 4.7, but it sounds like it also comes
with some bugs. I have been unable to determine the current status of
the divider option in the latest 4.7 kernel update. I have
experimented with "divider=10" and it works with no major problems,
except that the guest clock drifts ahead very slightly. So far, it
looks like several seconds of drift per day. Not a show-stopper, but
still a concern. With HZ=100, our time sync was spot on. In both cases
we are using "clock=pit nosmp noapic" and tools.syncTime="TRUE". If it
matters, our host machines are CentOS 4.6 x86_64.

Can anyone comment on the current status of bugs with the divider
option? Is anyone getting accurate time sync with divider=10 with
2.6.9-78.0.1? Is there anything else to watch out for? Is there any
fix for the slight time drift with divider=10?

I am primarily concerned with i686.

Currently, the SRPM for -78.0.1 is missing from the mirrors, so if I
want to update, I have to rely on the divider option for my VMware
guests. It also appears that Tru has not yet added any -78 RPMs to his
kernel-vm project.