This is when I patch the UML kernel with the NO_HZ patches that you put up last month.. on 2.6.23-rc6-mm1. Powertop is running on the host kernel and tells you which process wake up the processor from idle the most and also which the offending function is (in this case, it shows it to be do_nanosleep()). Yup this is a bad thing from the power consumption viewpoint and you would like the processor to be in higher C-states most of the time.

On 10/17/07, Jeff Dike <> wrote:
On Tue, Oct 16, 2007 at 10:36:39PM -0400, Hrishikesh wrote:
> When running powertop, I notice that there is a dramatic drop in C3 state
> residency when running the patched kernel. This happens when you run a
> patched kernel but without the NO_HZ and HR timers options disabled. C3
> state residency drops from about 90% to 50% when the UML kernel is idle.
> This does not happen when the tickless option _is_ enabled.

Which kernel is the patched kernel, the host or UML?

Whichever kernel this is, I take it that this is a bad thing?


Work email - jdike at linux dot intel dot com