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

[Avi Kivity]

On 02/02/2012 07:51 PM, Paul E. McKenney wrote:
> 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?
>

Looks like there are new rcu_user_enter() and rcu_user_exit() APIs which
we can use.  Hopefully they subsume rcu_virt_note_context_switch() so we
only need one set of APIs.

-- 
error compiling committee.c: too many arguments to function

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