Date: Sun, 22 Oct 2017 10:02:24 -0600 From: Ian Lepore <ian@freebsd.org> To: Boris Samorodov <bsam@passap.ru>, Michael Voorhis <mvoorhis@mcvau.net> Cc: freebsd-current@FreeBSD.org, freebsd-virtualization@FreeBSD.org Subject: Re: host, bhyve vm and ntpd Message-ID: <1508688144.1383.114.camel@freebsd.org> In-Reply-To: <6dc189a0-e7bc-6c3b-2be6-80154e7ece42@passap.ru> References: <2931f1cc-6574-b58d-4b94-5f77fa5cdb85@passap.ru> <1508512327.1383.55.camel@freebsd.org> <39bf2426-2edf-d485-7c81-519e931154be@passap.ru> <bf8eae88-ee44-58d5-bb3a-565a0314fdfe@passap.ru> <1508517160.1383.63.camel@freebsd.org> <76ff7afb-3d3a-96f6-1275-89472ff5683d@passap.ru> <1508522667.1383.69.camel@freebsd.org> <30992c14-7b78-ab9f-5693-931e6ca41f1b@passap.ru> <1508523696.1383.75.camel@freebsd.org> <23019.46875.929719.481108@atom.mcvau.net> <1508624153.1383.107.camel@freebsd.org> <6dc189a0-e7bc-6c3b-2be6-80154e7ece42@passap.ru>
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On Sun, 2017-10-22 at 11:31 +0300, Boris Samorodov wrote: > 22.10.2017 01:15, Ian Lepore ÐÉÛÅÔ: > > > > On Sat, 2017-10-21 at 17:07 -0400, Michael Voorhis wrote: > > > > > > Ian Lepore writes: > > > > > > > > > > > > Beyond that, I'm not sure what else to try. šIt might be necessary to > > > > get some bhyve developers involved (I know almost nothing about it). > > > NTPD behaves more normally on uniprocessor VMs. > > > > > > A FreeBSD bhyve-guest running on a freebsd host will select a > > > different timecounter depending on whether it is a multiprocessor or a > > > uniprocessor.ššMy uniprocessor bhyve-vm selected TSC-low as the best > > > timecounter in a uniprocessor.ššNTP functions there as expected. > > > > > > kern.timecounter.choice: TSC-low(1000) ACPI-fast(900) HPET(950) i8254(0) dummy(-1000000) > > > kern.timecounter.hardware: TSC-low > > > > > > The very same VM, when given two total CPUs, selected HPET (if I > > > recall) and the timekeeping with NTPD was unreliable, with many > > > step-resets to the clock. > > > > > Hmm, I just had glance at the code inšsys/amd64/vmm/io/vhpet.c and it > > looks right. šI wonder if this is just a simple roundoff error in > > converting between 10.0MHz and SBT units? šIf so, that could be wished > > away easily by using a power-of-2 frequency for the virtual HPET. šI > > wonder if the attached patch is all that's needed? > I've tried the patch (at bhyve guest) and nothing has changed. Should > the patched system be tested at bhyve guest or bhyve host? > Oh, I'm sorry, I should have mentioned that's for the host side. -- Ian
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