On Wed, Sep 17, 2008 at 11:23 AM, Jeff <jlar310 at gmail.com> wrote: > 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. As far as I can tell from my limited experience, the clock issue occurs regardless of the method taken, namely, kernel-vm (100Hz kernel) or divider=10. (Of course, this is with older kernels, not -78) Both options work fine when it comes to idle %cpu. One improvement of the 4.7 kernel is that it does not crash even when divider= is used together with clock=pit like it does with CentOS-5 kernels. Yes, the srpm file for -78.0.1 is missing (see http://bugs.centos.org/view.php?id=3132 ). But we can try -78 for performing a test. Akemi