On Sun, Feb 05, 2012 at 08:59:27AM -0800, Paul E. McKenney wrote: > On Sun, Feb 05, 2012 at 02:16:17PM +0200, Avi Kivity wrote: > > 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. > > Now that you mention it, that is a good goal. However, it requires > coordination with Frederic's code as well, so some investigation > is required. Bad things happen if you tell RCU you are idle when you > really are not and vice versa! > > Thanx, Paul > Right. Avi I need to know more about what you need. rcu_virt_note_context_switch() notes a quiescent state while rcu_user_enter() shuts down RCU (it's in fact the same thing than rcu_idle_enter() minus the is_idle_cpu() checks). -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>