Date: Wed, 27 Jun 2018 10:14:37 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: FreeBSD Current <freebsd-current@FreeBSD.org> Subject: TSC calibration in virtual machines Message-ID: <8ac353c5-d188-f432-aab1-86f4ca5fd295@FreeBSD.org>
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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 -- Andriy Gapon
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