Re: [GIT PULL] First batch of KVM changes for 4.1

Peter Zijlstra
2015-04-17T13:43:51Z

On Fri, Apr 17, 2015 at 03:38:58PM +0200, Paolo Bonzini wrote:
> > The path this notifier is called from has nothing to do with those
> > costs.
>
> How not? The task is going to incur those costs, it's not like half
> a dozen extra instruction make any difference. But anyway...

Its attributed to the entity doing the migration, which can be the
wakeup path or a softirq. And we very much do care about the wakeup
path.

> ... that's a valid objection. Please look at the patch below.

Still a NAK on that, distros have no choice but to enable that CONFIG
option because people might want to run KVM.

CONFIG options are pointless if they end up being mandatory.