Re: [v7 0/8] Reduce cross CPU IPI interference

From: Paul E. McKenney
Date: Thu Feb 02 2012 - 12:52:13 EST

On Thu, Feb 02, 2012 at 07:23:39PM +0200, Avi Kivity wrote:
> On 02/02/2012 07:01 PM, Paul E. McKenney wrote:
> > >
> > > It's not called (since the cpu is not idle). Instead we call
> > > rcu_virt_note_context_switch().
> >
> > Frederic's work checks to see if there is only one runnable user task
> > on a given CPU. If there is only one, then the scheduling-clock interrupt
> > is turned off for that CPU, and RCU is told to ignore it while it is
> > executing in user space. Not sure whether this covers KVM guests.
> Conceptually it's the same. Maybe it needs adjustments, since kvm
> enters a guest in a different way than the kernel exits to userspace.
> > In any case, this is not yet in mainline.
> Let me know when it's in, and I'll have a look.

Could you please touch base with Frederic Weisbecker to make sure that
what he is doing works for you?

Thanx, Paul

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