On Wed, Jun 27, 2018 at 10:36 AM, Jung-uk Kim <jkim_at_freebsd.org> wrote: > On 06/27/2018 03:14, Andriy Gapon wrote: > > > > It seems that TSC calibration in virtual machines sometimes can do more > harm > > than good. Should we default to trusting the information provided by a > hypervisor? > > > > Specifically, I am observing a problem on GCE instances where calibrated > TSC > > frequency is about 10% lower than advertised frequency. And apparently > the > > advertised frequency is the right one. > > > > I found this thread with similar reports and a variety of workarounds > from > > administratively disabling the calibration to switching to a different > timecounter: > > https://lists.freebsd.org/pipermail/freebsd-cloud/2017- > January/000080.html > > We already do that for VMware hosts since r221214. > > https://svnweb.freebsd.org/changeset/base/221214 > > We should do the same for each hypervisor. > > Jung-uk Kim > > We probably should. But why does calibration fail in the first place? If it can fail in a VM, then it can probably fail on bare metal too. It would be worth investigating.Received on Wed Jun 27 2018 - 14:47:54 UTC
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