Re: host, bhyve vm and ntpd

On Fri, 2017-10-20 at 18:36 +0300, Boris Samorodov wrote:
> 20.10.2017 18:31, Boris Samorodov пишет:
> > 
> > 20.10.2017 18:12, Ian Lepore пишет:
> > > 
> > > On Fri, 2017-10-20 at 14:46 +0300, Boris Samorodov wrote:
> > > > 
> > > > Hi All,
> > > > 
> > > > I have got a host:
> > > > ---
> > > > bhyve-host% uname -a
> > > > FreeBSD sm.bsnet 12.0-CURRENT FreeBSD 12.0-CURRENT #3 r322868: Fri Aug
> > > > 25 05:25:26 MSK 2017
> > > > bsam_at_builder.bsnet:/usr/obj/usr/src/sys/GENERIC-FAST  amd64 amd64
> > > > ---
> > > > 
> > > > And a bhyve vm:
> > > > ---
> > > > bhyve-vm: uname -a
> > > > FreeBSD builder.bsnet 12.0-CURRENT FreeBSD 12.0-CURRENT #58 r324782: Fri
> > > > Oct 20 05:12:17 MSK 2017
> > > > bsam_at_builder.bsnet:/usr/obj/usr/src/sys/PKG64X  amd64 amd64
> > > > ---
> > > > 
> > > > The only difference at kernel configs is a colored console. :-)
> > > > 
> > > > And here I get some weird (is it?) result at the VM (I expect ntpd to be
> > > > more stable):
> > > > ---
> > > > bhyve-vm% for t in `jot 10`; do ntpq -pn; sleep 64; done
> > > >      remote           refid      st t when poll reach   delay   offset
> > > > jitter
> > > > ==============================================================================
> > > >  XX.XX.XX.1      XX.XX.XX.245     4 u    9   64    3    0.605   -1.202
> > > > 316.407
> > > >  XX.XX.XX.1      XX.XX.XX.245     4 u    7   64    7    0.605   -1.202
> > > > 358.395
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u    5   64   17    0.615  -328.42
> > > > 181.405
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u    3   64   37    0.615  -328.42
> > > > 214.868
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u   67   64   37    0.615  -328.42
> > > > 214.868
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u   63   64   77    0.615  -328.42
> > > > 268.618
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u   60   64  177    0.615  -328.42
> > > > 333.175
> > > >  XX.XX.XX.1      .STEP.          16 u 1910   64    0    0.000    0.000
> > > > 0.000
> > > >  XX.XX.XX.1      XX.XX.XX.245     4 u   27   64    1    0.703  -262.63
> > > > 0.004
> > > >  XX.XX.XX.1      XX.XX.XX.245     4 u   31   64    1    0.649  -331.43
> > > > 68.800
> > > > ---
> > > > 
> > > > At the same time host's results are very stable:
> > > > ---
> > > > bhyve-host% for t in `jot 10`; do ntpq -pn; sleep 64; done
> > > >      remote           refid      st t when poll reach   delay   offset
> > > > jitter
> > > > ==============================================================================
> > > > 
> > > > 
> > > > 
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u    1   64    1    0.401    0.176
> > > > 0.106
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u    6   64    3    0.401    0.176
> > > > 0.459
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u    3   64    7    0.401    0.176
> > > > 0.940
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u   67   64    7    0.401    0.176
> > > > 0.940
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u   64   64   17    0.401    0.176
> > > > 1.566
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u   60   64   37    0.448    1.275
> > > > 1.739
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u   55   64   77    0.448    1.275
> > > > 2.365
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u   53   64  177    0.448    1.275
> > > > 3.110
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u   50   64  377    0.448    1.275
> > > > 3.929
> > > > *XX.XX.XX.1      XX.XX.XX.245     4 u   45   64  377    0.443    8.750
> > > > 4.722
> > > > ---
> > > > 
> > > > The network is organized via bridge -- host igb and vm tap interfaces
> > > > are members of one bridge.
> > > > 
> > > > Are those results expected? Does it smell like a bug? Should I dig
> > > > furter?
> > > > 
> > > So it is repeatedly stepping the clock in the VM? (Set
> > > kern.timecounter.stepwarnings=1 to log steps).
> > No kernel/ntpd messages for 20 minutes after setting this sysctl.
> > 
> > > 
> > >  That is usually a sign
> > > that the chosen timecounter is running at a different frequency than it
> > > claimed to be when it registered itself -- the host may not be
> > > emulating the timer hardware properly in the guest.  What is the output
> > > of sysctl kern.timecounter in the vm?
> > ---
> > bhyve-vm% sysctl kern.timecounter
> > 
> > kern.timecounter.tsc_shift: 1
> > kern.timecounter.smp_tsc_adjust: 0
> > kern.timecounter.smp_tsc: 0
> > kern.timecounter.invariant_tsc: 1
> > kern.timecounter.fast_gettime: 1
> > kern.timecounter.tick: 1
> > kern.timecounter.choice: ACPI-fast(900) HPET(950) i8254(0) TSC-low(-100)
> > dummy(-1000000)
> > kern.timecounter.hardware: HPET
> > kern.timecounter.alloweddeviation: 5
> > kern.timecounter.stepwarnings: 1
> > kern.timecounter.tc.ACPI-fast.quality: 900
> > kern.timecounter.tc.ACPI-fast.frequency: 3579545
> > kern.timecounter.tc.ACPI-fast.counter: 4161213491
> > kern.timecounter.tc.ACPI-fast.mask: 4294967295
> > kern.timecounter.tc.HPET.quality: 950
> > kern.timecounter.tc.HPET.frequency: 10000000
> > kern.timecounter.tc.HPET.counter: 3518036865
> > kern.timecounter.tc.HPET.mask: 4294967295
> > kern.timecounter.tc.i8254.quality: 0
> > kern.timecounter.tc.i8254.frequency: 1193182
> > kern.timecounter.tc.i8254.counter: 47597
> > kern.timecounter.tc.i8254.mask: 65535
> > kern.timecounter.tc.TSC-low.quality: -100
> > kern.timecounter.tc.TSC-low.frequency: 1199886114
> > kern.timecounter.tc.TSC-low.counter: 1274338278
> > kern.timecounter.tc.TSC-low.mask: 4294967295
> > ---
> BTW, here is the host kern.timecounter:
> ---
> kern.timecounter.tsc_shift: 1
> kern.timecounter.smp_tsc_adjust: 0
> kern.timecounter.smp_tsc: 1
> kern.timecounter.invariant_tsc: 1
> kern.timecounter.fast_gettime: 1
> kern.timecounter.tick: 1
> kern.timecounter.choice: ACPI-fast(900) HPET(950) i8254(0) TSC-low(1000)
> dummy(-1000000)
> kern.timecounter.hardware: TSC-low
> kern.timecounter.alloweddeviation: 5
> kern.timecounter.stepwarnings: 0
> kern.timecounter.tc.ACPI-fast.quality: 900
> kern.timecounter.tc.ACPI-fast.frequency: 3579545
> kern.timecounter.tc.ACPI-fast.counter: 9047194
> kern.timecounter.tc.ACPI-fast.mask: 16777215
> kern.timecounter.tc.HPET.quality: 950
> kern.timecounter.tc.HPET.frequency: 14318180
> kern.timecounter.tc.HPET.counter: 2232552795
> kern.timecounter.tc.HPET.mask: 4294967295
> kern.timecounter.tc.i8254.quality: 0
> kern.timecounter.tc.i8254.frequency: 1193182
> kern.timecounter.tc.i8254.counter: 43410
> kern.timecounter.tc.i8254.mask: 65535
> kern.timecounter.tc.TSC-low.quality: 1000
> kern.timecounter.tc.TSC-low.frequency: 1200067168
> kern.timecounter.tc.TSC-low.counter: 2463146362
> kern.timecounter.tc.TSC-low.mask: 4294967295
> ---
> 
> > 
> > > 
> > > Also, what is the output of ntptime(8) in the vm?
> > ---
> > bhyve-vm% ntptime
> > 
> > ntp_gettime() returns code 0 (OK)
> >   time dd94930f.20ea2900  Fri, Oct 20 2017 18:21:51.128, (.128573699),
> >   maximum error 1309110 us, estimated error 3 us, TAI offset 37
> > ntp_adjtime() returns code 0 (OK)
> >   modes 0x0 (),
> >   offset 0.000 us, frequency 0.000 ppm, interval 1 s,
> >   maximum error 1309110 us, estimated error 3 us,
> >   status 0x2001 (PLL,NANO),
> >   time constant 6, precision 0.001 us, tolerance 496 ppm,
> > ---
> > 
> > Ian, thank you for your help!
> > 
> 

It seems odd to me that the frequency of the host HPET is 14.3mhz and
that of the guest is 10.0mhz, but maybe that's a normal condition for
bhyve.  I did find some google hits[1] for bhyve guest timekeeping
trouble with the HPET timer which was solved by switching to a
different timecounter.  Timecounter choices can't be controlled from
loader.conf, so I guess a sysctl.conf entry of
kern.timecounter.hardware="ACPI-fast" is the only way to fix that.  You
can also just do that command interactively first and see if it stops
the time steps and ntp settles down.

This would be a workaround, not a fix per se.  If the time steps go
away, then something in bhyve's emulation of HPET (maybe only on some
hardware?) must be buggy.


[1] https://lists.freebsd.org/pipermail/freebsd-virtualization/2015-April/003492.html

-- Ian