-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 02/06/2015 08:46 AM, Frederic Weisbecker wrote: > On Thu, Feb 05, 2015 at 03:23:47PM -0500, riel@xxxxxxxxxx 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. That said it's > potentially interesting to turn off the tick on the host when the > guest runs. > >> , and the KVM guest running with idle=poll mode, we still get >> wakeups of the rcuos/N threads. > > So we need nohz_full on the host and idle=poll mode on the guest. > Is it likely to happen? (sorry, again I'm just trying to make sure > we agree on why we do this change). We have users interested in doing just that, in order to run KVM guests with the least amount of perturbation to the guest. - -- All rights reversed -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJU1NYrAAoJEM553pKExN6DMgcIAIKoBBxsFEt7yOP+k32uqm+W S/VbP5dIHE5OnYeBoitgNkia1U4rsAX6AVAuVFvKc7Y8aixENGzubPWHe0NuHida VIaQmK92Jym4FH8Xsnj09MhgLV+ZEG/cCzdUFZfShJq3hHwzedZx+cC7uQMB6kd4 iuo7CtgTjzTgBce29Fc147azXlJbfFfwFt3a6YVxbv25IYpDL9ETulh34h6NrNLz nB0snDjq8FHKcyjlD3XnJpT/tbaZcrZctExq4JrespcBMe6prMnoWvVoXWX/fVVG TIR1hp2xfKWoS4gc56PnLazIIB9SRmlC/SzSMwAaSgf1dWa5BcwpuMbYVFIEeME= =+BrK -----END PGP SIGNATURE----- -- 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
