On Fri, 28 Aug 2009, Thomas Gleixner wrote:

The statistics stuff needs to be tackled anyway as we need to offload
the sched accounting to some other cpu.

The vm statisticcs in mm/vmstat.c are different from the sched accounting.

What slab queue stuff is running on timers and cannot be switched off
in such a context?

slab does run a timer every 2 second to age queues. If there was activity
then there can be a relatively long time in which we periodically throw
out portions of the cached data.

Device specific stuff should not happen on such a CPU when there is no
device handled on it.

The device may periodically check for conditions that require action.