On Fri, Feb 06, 2015 at 02:50:44PM +0100, Paolo Bonzini wrote: > > > On 06/02/2015 14:46, Frederic Weisbecker wrote: > > > When running a KVM guest on a system with NOHZ_FULL enabled > > > > I just need to clarify the motivation first, does the above situation > > really happen? Ok some distros enable NOHZ_FULL to let the user stop > > the tick in userspace. So most of the time, CONFIG_NOHZ_FULL=y but > > nohz full is runtime disabled (we need to pass a nohz_full= boot > > parameter to enable it). And when it is runtime disabled, there should > > be no rcu nocb CPU. > > > > (Although not setting CPUs in nocb mode when nohz full is runtime disabled > > is perhaps a recent change.) > > > > So for the problem to arise, one need to enable nohz_full and run KVM > > guest. And I never heard about such workloads. > > Yeah, it's a new thing but Marcelo, Luiz and Rik have been having a lot > of fun with them (with PREEMPT_RT too). They're getting pretty good > results given the right tuning. > > I'll let Paul queue the patches for 3.21 then! Frederic, given the background from Paolo, Rik, and Christian, are you OK with these patches? Thanx, Paul > Paolo > > > That said it's potentially > > interesting to turn off the tick on the host when the guest runs. > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
