From mboxrd@z Thu Jan 1 00:00:00 1970 From: Frederic Weisbecker Subject: Re: [PATCH -v5 0/5] rcu,nohz,kvm: use RCU extended quiescent state when running KVM guest Date: Thu, 12 Feb 2015 18:09:12 +0100 Message-ID: <20150212170909.GI18363@lerouge> References: <1423600074-2907-1-git-send-email-riel@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: paulmck@linux.vnet.ibm.com, luto@amacapital.net, will.deacon@arm.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, mtosatti@redhat.com, borntraeger@de.ibm.com, lcapitulino@redhat.com, pbonzini@redhat.com To: riel@redhat.com Return-path: Content-Disposition: inline In-Reply-To: <1423600074-2907-1-git-send-email-riel@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Tue, Feb 10, 2015 at 03:27:49PM -0500, riel@redhat.com wrote: > When running a KVM guest on a system with NOHZ_FULL enabled, and the > KVM guest running with idle=poll mode, we still get wakeups of the > rcuos/N threads. > > This problem has already been solved for user space by telling the > RCU subsystem that the CPU is in an extended quiescent state while > running user space code. > > This patch series extends that code a little bit to make it usable > to track KVM guest space, too. > > I tested the code by booting a KVM guest with idle=poll, on a system > with NOHZ_FULL enabled on most CPUs, and a VCPU thread bound to a > CPU. In a 10 second interval, rcuos/N threads on other CPUs got woken > up several times, while the rcuos thread on the CPU running the bound > and alwasy running VCPU thread never got woken up once. > > Thanks to Christian Borntraeger, Paul McKenney, Paulo Bonzini, > Frederic Weisbecker, and Will Deacon for reviewing and improving > earlier versions of this patch series. > So the patchset look good, thanks everyone. I'm applying the series and will see anything explode. I'll wait until the end of the merge window to push it to Ingo. Thanks.