On Tue, May 27, 2008 at 3:33 PM, Ruslan Sivak russ@vshift.com wrote:
Akemi Yagi wrote:
On Tue, May 27, 2008 at 1:07 PM, Tom Bishop bishoptf@gmail.com wrote:
OK, so I need to bring up a new vm and was wondering what the state of vm kernels for centos. I have read this http://bugs.centos.org/view.php?id=2189 about the tick divider but it wasn't clear what the best step forward is for centos 5.1 was, i usually ran with the clocksource=pit option and it looked like that and the divider option caused a problem. I have in the past compiled my own but was wondering what others were now doing, thanks in advance 8-)
Thanks to Tru, kernel-vm is all up-to-date and you can find it here:
http://people.centos.org/tru/kernel-vm/
and yes, using the clocksource=pit option should not be an issue with these kernels.
Akemi
So if I understand this correctly, one should not be using a stock kernel when running inside a vm, but should use the kernel-vm kernel?
Russ
You *can* run the distro kernel inside a vm. The CentOS bug entry referred to by the original poster explains in great details why a kernel with 100hz clock rate (kernel-vm) gives you improved performance compared to the distro standard kernel (1000hz) and handles clock drifts better. Recent distro kernels offer a new kernel option "divider=" that lets you reduce the clock rate. This should eventually eliminate the need for the kernel-vm. However, at the moment, the divider= option has a bug that causes problems when it is combined with clocksource=pit. And the timer "pit" is often used when the system clock tends to go faster.
Akemi