On Wed, 2009-09-16 at 20:58 +0530, Dipankar Sarma wrote:

On Tue, Sep 15, 2009 at 02:11:41PM +0200, Peter Zijlstra wrote:

quoted

On Tue, 2009-09-15 at 17:36 +0530, Gautham R Shenoy wrote:

quoted

This patchset contains the offline state driver implemented for
pSeries. For pSeries, we define three available_hotplug_states. They are:

        online: The processor is online.

        offline: This is the the default behaviour when the cpu is offlined

        inactive: This cedes the vCPU to the hypervisor with a cede latency

Any feedback on the patchset will be immensely valuable.

I still think its a layering violation... its the hypervisor manager
that should be bothered in what state an off-lined cpu is in. 

The problem is that all hypervisor managers cannot figure out what sort
of latency guest OS can tolerate under the situation. They wouldn't know
from what context guest OS has ceded the vcpu. It has to have
some sort of hint, which is what the guest OS provides.

I'm missing something here, hot-unplug is a slow path and should not
ever be latency critical..?